Political commentator Rush Limbaugh (search) returned to his popular radio program Friday and said he was "frustrated" about allegations that he was involved in the sale and use of illegal drugs.

Limbaugh was back on the air one day after his name surfaced as the possible target of a criminal probe into the sale and use of illegal drugs in south Florida.

On the national program, which is carried by about 650 stations across the country, Limbaugh spoke briefly about the allegations of his drug use but avoided going into specifics. He said he was "a little frustrated" that he had not "gotten to the bottom" of what was happening.

"The story in Florida really is an emerging situation ... I don't really know the full scope of what I'm dealing with," he said. Limbaugh said he'd been humbled by all the supportive e-mails he'd received from fans, estimating he'd received about 25,000.

As for all the media stories that have emerged about the drug investigation, Limbaugh said that he was "tempted" to respond to them but "I'm not going to go there."

But he vowed to discuss the case in detail in the future.

"Rest assured, I will discuss this with you and tell you how it is ... maybe more than you really want to know about this," he said.

Limbaugh's official Web site, RushLimbaugh.com, broadcast his national radio show beginning at noon EDT Friday.

In a statement issued Thursday, Limbaugh said he was unaware of any investigation involving him. "No government representative has contacted me directly or indirectly. If my assistance is required, I will, of course, cooperate fully," he said.

Limbaugh has hired noted defense lawyer Roy Black, sources told Fox News. Black defended William Kennedy Smith, who was acquitted of rape charges in 1991.

The drug claims were only part of the scandal surrounding the controversial radio host that broke this week. Late on Wednesday, Limbaugh quit his job as a football analyst for ESPN after he came under fire for making comments about Philadelphia Eagles quarterback Donovan McNabb (search), the media and race.

Limbaugh, who was criticized for suggesting that sports reporters were building up McNabb simply because he was a black quarterback, said during his radio show that he had nothing to apologize for.

"I know I'm right about this. I'm not going to retract anything," Limbaugh said Friday.

• Video: Rush Under Fire

Drug Allegations Began With Former Housekeeper 

Limbaugh apparently had multiple sources from whom he could illegally obtain the prescription drugs, namely OxyContin (search) and two other painkillers, law enforcement sources told Fox News on Thursday.

OxyContin is a pain reliever that contains a very strong narcotic similar to morphine and is only intended for moderate to severe daily pain, according to the Food and Drug Administration. The two other painkillers Limbaugh allegedly obtained were Lorcet (search) and Hydrocone (search), two medications that can damage hearing, sources told Fox News.

In 2001, Limbaugh discovered that his hearing was quickly disappearing. At one point, he used an elaborate setup at his South Florida studio involving transcribers and computer screens to read listeners' calls. He had an electronic device placed in his skull to help restore his hearing.

Reports in the New York Daily News and the National Enquirer alleged Limbaugh got the drugs from his housekeeper, Wilma Cline (search), who in some cases hid the drugs under Limbaugh's bed.

Cline told authorities that some of the drug handoffs took place at a gas station in West Palm Beach, Fla. Limbaugh allegedly would pull up in his car and Cline would hand over a cigar box full of pills in exchange for cash, sources told Fox News.

But sources close to the investigation told Fox News that Limbaugh had other drug suppliers and said the popular conservative personality could face a criminal inquiry by the Palm Beach County (search) state attorney's office.

Cline's attorney, Ed Shohat, told Fox News that "my client stands behind her story." Cline has been granted immunity from prosecution in exchange for her cooperation, a source told Fox News.

The investigation apparently began as a probe into the illegal sale of prescription painkillers in South Florida that targeted dealers. But later investigators came across Limbaugh through clues gathered in a bust in Palm Beach County in May, revealing him as a buyer.

One source told Fox News that Limbaugh was implicated by Cline and her husband David, and also by “other suppliers” whom the source did not name. The Enquirer paid the Clines a six-figure fee for their story, according to the source.

Asked about the culpability of Limbaugh, the source said that he could still face charges for having a large quantity of prescription painkillers without a prescription, but the source added that no charges are imminent.

Fox News' Orlando Salinas, J. Jennings Moss, Catherine Donaldson-Evans and The Associated Press contributed to this report.