Authorities have launched a criminal investigation into suspected dumping of homeless people on Skid Row after police witnessed ambulances leaving five people on a street there during the weekend.

The city attorney's office is reviewing police videotapes and photographs of the five alleged dumping cases Sunday to determine whether the patients were falsely imprisoned during their transfer and whether the hospital, Los Angeles Metropolitan Medical Center, violated any laws regarding the treatment of patients.

Two of the patients told officers they did not want to be taken downtown, said police Capt. Andrew Smith.

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"There is an expression in the medical profession that is something to the effect of 'Do no harm,"' Chief William Bratton said at a press conference. "When a hospital or an ambulance service takes an individual into Skid Row and leaves them and drives off, they are subjecting that person to considerable risk."

Police have long suspected that several institutions, including law enforcement agencies from outside Los Angeles, were using downtown's Skid Row as a dumping ground for homeless people.

Officials from the Los Angeles Metropolitan Medical Center denied they had improperly handled the patients.

"With all of the issues, why would we send someone there who did not ask to go there? It is illogical," John V. Fenton, president and chief executive of Los Angeles Metropolitan Medical Center, said in an interview with the Los Angeles Times.

James Fraley, an attendant with ProCare, a private ambulance company, told police the hospital had hired his company to move discharged patients from the medical center to Skid Row, the newspaper said.

Skid Row has one of the nation's largest concentrations of homeless people, in part because it has a cluster of shelters and services to help them. For decades the 50-square-block neighborhood also has been an open-air market for drugs and prostitution — policed, in large part, with a policy of containment.

But the city in recent weeks has begun enforcing laws in the area with a new vigor, as nearby neighborhoods that were once run down are enjoying a surge of new luxury apartments, hotels and cultural offerings.

Bratton said 50 new officers charged with patrolling Skid Row will remain on the lookout for dumping of homeless patients.

"We're in this to solve this and we're not going away," he said.

Two of the new foot patrol officers made the discovery that led to the Police Department's first criminal probe into the practice.

The investigation began on Sunday, when a police sergeant saw a patient being left in front of the Volunteers of America homeless services facility. The sergeant called a police videographer, who over the next few hours recorded four more ambulances arriving at the facility and leaving recently discharged patients.

Smith, commanding officer of the Police Department's central area, said supervising officers took one of the patients home, where the man's family was angered.

"His family was outraged," Smith told the news conference. "Not only did they not know that he was discharged but the fact that he had been brought to Skid Row instead of being brought home was what further outraged that family."

Fenton said three of the five patients had arrived at the hospital from Volunteers of America or the nearby Lamp Community center, and gave the street addresses on their admission information.

Officials at Lamp and Volunteers of America, however, said they had no record of any of the five patients having been at their facilities.

No law prevents hospitals from sending patients to Skid Row after they've been discharged.

But the city attorney is investigating whether taking homeless people from a hospital to Skid Row would violate federal laws against releasing or transferring patients who are medically unstable and whether hospitals can be sued for unscrupulous behavior.

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