As police tried to determine whether a self-proclaimed mercy killer was a mass murderer or a fraud, people came forward Saturday to tell police their relatives died mysteriously at a hospital that employed him.

"Their loved ones seemed to be OK one day and gone the next," said Rick Young, spokesman for the Glendale Police Department, which is heading the investigation into the claims by the former respiratory therapist at Glendale Adventist Medical Center.Police were still unsure if Efren Saldivar, who is in his 20s and lives in Los Angeles, told the truth when he admitting killing 40 to 50 terminally ill patients in the past decade.

"We must establish that a crime did in fact occur," Young said.

Saldivar hasn't been charged with a crime and remains free while police, prosecutors and medical regulators continue with their investigations. His license was suspended March 13, regulators announced Friday.

Inundated with calls from the media and relatives, the 450-bed, 1,800-employee hospital in the Los Angeles suburb distributed a letter to all of its patients Saturday to outline the allegations and explain why it suspended its entire 44-member respiratory care department.

"We want to assure you that we firmly believe there is no reason for concern regarding safety," it said. "We have taken every reasonable precaution to protect patients, and we are committed to doing whatever it takes to get to the truth in this investigation."

Saldivar told a police investigator earlier this month that he was an "angel of death" who killed patients he deemed to be on the verge of dying anyway through suffocation or drug injection, state medical regulators said.

Friday's announcement, in response to media calls to the state Respiratory Care Board, caught investigators by surprise, Young said.

"We were angry to begin with, and now we are totally frustrated as it has hampered this investigation 100 times fold," said Young, who noted that some hospital employees have become reluctant to cooperate for fear their names will be revealed.

Kathleen McCoy, executive officer of the state's Respiratory Care Board, which released the documents, responded that they officially became public once an administrative law court suspended Saldivar's license for 30 days. The court placed no secrecy order on the documents.

"We did not want to hamper their investigation, but these are public documents," McCoy said.

Saldivar faces a hearing Tuesday on whether regulators may permanently suspend his license.

He was jailed earlier this month but released two days later for lack of evidence pending further investigation - a situation that legal analysts say is not uncommon.

"If they don't believe he's a flight risk, they are better off releasing him and developing a case that will actually stick than holding him on superficial charges," said Carol Chase, a law professor at Pepperdine University.