No fewer than nine doctors from California, New York, Nevada, Texas and Florida — some of whom have been sanctioned or suspended by their state medical boards — are at the center of an extensive prescription drug probe as investigators try to piece together Michael Jackson’s medical history, FOXNews.com has learned.

After two weeks of rumors, theories and speculation, the official cause of Jackson’s death on June 25 will soon be made public. “We’re still on track and hope to be able to announce something as early as next week,” Assistant Chief Coroner Ed Winter told FOXNews.com.

But Jackson, who was 50 and in apparently good condition, was a known abuser of prescription drugs, especially painkillers, and there has been widespread speculation that those drugs will be found to have contributed to – if not caused – his death. Los Angeles police detectives are currently investigating the numerous medications Jackson was known to have taken and the doctors who provided them – an investigation that could go on for years.

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Among the physicians known or believed to have treated Jackson over the last several years are:

— Dr. Alimorad "Alex" Farschchian, family practitioner, dispensing practitioner, runs the Center for Regenerative Medicine in Miami Beach, Fla.

— Dr. Allan Metzger, Lupus specialist, internist, rheumatologist, has a practice in West Hollywood, Calif.

— Dr. William Barnhart “Barney” VanValin, internist and general practitioner, specializing in thyroid problems, staff doctor at the Hormone Resource Center in Solvang, Calif.

— Dr. Cary Phillip Logan, internist, general practitioner, concierge physician, Inn-House Doctor, Inc., in Las Vegas.

— Dr. Neil Ratner, anesthesiologist, Woodstock, N.Y.

— Dr. Saunders, no other information available.

— Dr. Gerald Labiner, recently retired, practiced in Beverly Hills.

— Dr. Conrad Murray, cardiologist, runs a private practice in Las Vegas and a clinic in Houston, was Jackson's personal physician at the time of the pop star's death.

— Dr. Arnold Klein, dermatologist, Beverly Hills.

In Miami, local and federal law enforcement agents will assist Los Angeles investigators in looking into Farshchian, FOXNews.com has learned. The doctor's name appeared in police interviews of members of Jackson’s security detail that were conducted by the Santa Barbara Sheriff’s Department in 2004 in the wake of child-molestation allegations against the pop star. The records were obtained and cited first by TMZ; FOXNews.com obtained the records, which were authenticated by law enforcement officials.

In one interview, a former bodyguard, Michael LaPerruque, described Farshchian to investigators as “Jackson’s physician and family friend” who was “awestruck by Michael Jackson.” According to the police report of this interview, LaPerruque said he felt Farshchian “may have been overprescribing medication.”

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Farshchian, who graduated from Spartan Health Sciences University in St. Lucia in 1987, runs the Center For Regenerative Medicine in Miami Beach. In 2002 he wrote a letter to Jackson outlining a “5-7 day program” of Buprinex, a non-addictive painkiller similar to Demerol. "Buprinex is the potent narcotic I told you about last week. It is just like the D but better," Farshchian wrote.

The former Jackson bodyguard said he had picked up prescriptions for Jackson that were written for “Chris Carter,” the name of another member of Jackson’s security detail. He said there were “some doctors that were trying to get Jackson off Demerol. He said there was one doctor in Santa Barbara that was upset with Jackson because he had been self-injecting.”

According to police records of another interview conducted in 2004, Carter told investigators that he would pick up Xanax prescriptions for Jackson that were filled using aliases, often using the names of his staff. Carter also told police that Jackson was taking “10-plus Xanax pills a night,” but he had learned that “Jackson was doing better because he was down from 30 to 40 Xanax pills a night.” Carter said Farshchian told him that Jackson was addicted to Demerol.

Farshchian did not reply to requests for comment.

When asked if his office had received any medical records from Farshchian, Winter said, “Don’t know who that is,” before adding, “We’re not commenting.”

According to the same report, Carter also told police he would drive Jackson to doctors’ offices in New York, Florida and California for visits with “Dr. Klein, Dr. Metzger, Dr. Barney from Solvang, Dr. Saunders and Dr. Farshchian.”

Metzger was issued a public letter of reprimand by the California Medical Board in September 2000. It said, “You engaged in a fraudulent medical practice based on prescriptions written for an international entertainer using a false/fictitious name.”

Metzger confirmed to TMZ that the celebrity was Janet Jackson and that the prescriptions — for diuretics and a Hepatitis B shot — were written in the name of her personal chef. After Michael Jackson's death, Metzger issued a statement saying that he hadn’t spoken with the pop star in months and hadn't treated him in years.

"Barney" VanValin's name appears on prescription bottles of generic and brand Xanax filled in 2002 in the names of Frank Tyson and Manuel Rivera, who were members of Jackson’s staff, according to the same report and a police inventory of physical evidence recovered from Neverland Ranch in 2003. The evidence logs, which were obtained and authenticated by FOXNews.com, lists these prescriptions among those found in the upstairs library room in the video arcade area of Jackson's famed estate. Prescriptions written by the same doctor for Percocet were also found, according to the same report. VanValin, who graduated from Autonomous University of Guadalajara Faculty of Medicine in 1981, did not return messages left at his office.

In Las Vegas, where Jackson’s personal physician Dr. Murray, runs his cardiology practice, law enforcement sources told FOXNews.com that they are looking at another local doctor: Dr. Cary Phillip Logan, the medical director of a nationwide concierge practice called Inn-House Doctors, Inc. According to Inn-House's Web site, the company provides on-call physicians — the service employs roughly 40 doctors — in Atlanta, Boston, Chicago, Houston, Philadelphia, Las Vegas, Phoenix, Dallas, Washington, Baltimore, San Diego and Austin, Texas.

A bottle of antibiotics Logan prescribed to Jackson under the name “M.M” was found in the 2003 raid on Neverland, according to police inventory and evidence summary reports obtained by FOXNews.com.

In December 2005, Logan petitioned the Nevada State Board of Medical Examiners for “Consideration of Request to Prescribe to Hotel Guests Without Personal Contact With Those Guests."

According to open-session minutes of the board meeting, held over two days in the Tropicana Ballroom at the Las Vegas Embassy Suites Hotel:

“Cary Logan, M.D., Medical Director for Inn-House Doctor, explained that his company, currently offers medical care to Las Vegas visitors by providing phone consultations to those staying in area hotels. They triage patients over the phone and may either offer a medical visit or refer the patient to a medical facility if there is the need. Inn-House Doctor also has an agreement with pharmacies on the Las Vegas Strip to deliver prescriptions 24 hours a day. They want to expand their program to allow these pharmacies to provide a form to a patient who comes into the pharmacy with a problem that the patient would complete, which would include the patient’s medical history, and then send the form to a physician from Inn-House Doctor, who would review it and then talk with the patient over the phone and determine an appropriate course of care. The physician would then either refer the patient to a clinic, recommend a hotel visit by a physician, give a referral to an emergency room, or instruct the pharmacist to give the patient appropriate medication.”

The board unanimously voted to decline Logan’s request. Two board members “were both of the opinion that it is an unwise practice and a physician practicing in that manner would be leaving himself open to liability.”

Logandid not reply to requests for comment.

Sources said they were also interested in speaking to Ratner, an anesthesiologist who traveled with Jackson on tour about 10 years ago. Ratner's New York medical license was suspended for 36 months in July 2002 after he was convicted of federal criminal charges including mail fraud, health care craud and making false statements related to health care matters, according to the New York disciplinary board. He was sentenced to eight months, including four months of house arrest followed by three years of supervised release. According to New York state records, Ratner is currently allowed to practice.

Labiner's name was also found on bottles of prescription pills — including one for Percocet made out to a “Michael Armstrong” — in 2003 at Neverland Ranch, according to police evidence inventory reports obtained and verified by FOXNews.com. Records show that Labine recently retired his license in California, but it is unclear why. A graduate of the Indiana University School of Medicine in 1949, it’s possible that he retired.

The court papers summarizing police interviews with staff at Jackson’s Neverland Ranch also reference a “Dr. Saunders,” though details were not available.

Law enforcement sources confirmed to FOXNews.com that Demerol, propofol (Diprivan) alprazolam (Xanax), Percocet and antibiotics were found in Jackson’s rented Holmby Hills mansion after he died. At least some of the bottles of Diprivan recovered from Jackson’s home were found without labels indicating their origin.

Media reports have mentioned a laundry list of medications the King of Pop purportedly took in the days leading up to his death. They include the sedatives Zalepon, Eszopiclone and Zolpidem; painkillers OxyContin and Palladone; the antidepressants Prozac and Zoloft; stimulants, antibiotics; skin bleaching creams; and blood pressure medication.

Murray, who was at Jackson's side when the King of Pop went into cardiac arrest on June 25, is still the subject of police investigation. As FOXNews.com first reported, Murray was not licensed to prescribe controlled substances in California. The cardiologist, through his attorneys, has insisted that he did not give the star OxyContin or Demerol.

Klein, a dermatologist, has acknowledged giving Demerol to Jackson, but not Diprivan. He said he gave the King of Pop Demerol for sedation, and only on occasion. Klein said he found out Jackson was taking Diprivan when he was touring in Germany and warned his friend and patient of the dangers of the intravenously administered anesthetic. Neither Klein nor his attorney returned calls and e-mails seeking comment.

Dr. Len Horovitz, a pulmonary specialist at New York’s Lenox Hill Hospital who treated Jackson for dehydration in 1999, told FOXNews.com that the King of Pop showed him the medications he said he was on, and they included only antibiotics and skin cream. Horovitz said he hasn’t been contacted by anyone involved in the investigation, perhaps because he treated the star for a short time 10 years ago, and he didn’t prescribe any medicines. “Maybe they think I’m irrelevant,” he said, “But I would of course be willing to release records if asked.”