One source, who has seen one of the subpoenas, said it asked for 'any and all' of Jackson's medical records 'including radiology and psychiatric records.' An attorney for Dr. Arnold Klein, a Beverly Hills dermatologist who treated Jackson for nearly 25 years, said his client was among those receiving a formal request from the coroner's office. 'It was a standard form subpoena, and we turned over medical records to the medical examiner in response,' said lawyer Richard Charnley. The subpoenas come in addition to at least three search warrants issued last week as part of a Los Angeles Police Department probe into whether prescription drugs played a role in Jackson's death. Authorities have identified some of Jackson's doctors from the medications and other medical evidence they recovered from the home where Jackson was stricken June 25, according to sources familiar with the investigation. But those sources, who spoke on the condition that they not be named because it was an ongoing investigation, said some of the medication lacked prescription labels and that officials were trying to determine how Jackson obtained them. A longtime Jackson associate, who spoke on the condition that he not be named, said the pop star had little trouble finding doctors eager to treat him -- and prescribe him drugs. 'They rotate in and out,' said the source. 'There were a lot of doctors over the years. ... They liked to be known as Michael Jackson's doctor.' Experts said the task before detectives and coroner's investigators amounts to a medical jigsaw puzzle. They must gain a strong handle on his medical status at the time of his death, including pre-existing conditions, previous medical procedures and his drug-use history -- things that can be gleaned through many of the records requested and subpoenaed. After gathering information about what was prescribed and in what quantity, investigators with medical training look at the patient's history, the possible reasons each drug was prescribed, the side effects and the interactions with other medications. Investigators must also cross-reference medical files to try to recreate what a physician knew at the time he or she wrote a prescription. Ed Winter, assistant chief of the coroner's office, said the office does send subpoenas out in death investigations. 'In many cases, doctors will hand over the records,' he said. 'In some cases, they will ask us for a subpoena to get those records.' Winter would not comment on whether subpoenas were issued in Jackson's death. While officials are awaiting the results of toxicology tests conducted by the coroner's office the day after Jackson's death, they warn that those tests may not answer all the questions. For example, sources have told the Times that detectives found large amounts of the powerful anesthetic Diprivan at Jackson's home. But experts said that Diprivan moves through the body quickly and might not show up in some tests. Diprivan, which also goes by the generic name propofol, is an extremely potent drug that is supposed to be dispensed by a person trained to administer anesthesia. Paul Wischmeyer, an anesthesiologist at the University of Colorado who co-wrote a 2007 study of Diprivan abuse for the journal Anesthesia & Analgesia, said propofol would be 'probably undetectable' in the bloodstream in 20 minutes after a single dose. But he said that there are other ways that pathologists have used to identify presence of the drug in autopsies, if they know what to look for. 'You can find it in the urine,' Wischmeyer said. 'There's a test you have to know how to do. There aren't a lot of labs that know how to do it. But if you know, you can do it. ... It wouldn't be a test a coroner could do, but they could send out for it.' Staff writers Kimi Yoshino and Andrew Blankstein contributed to this report. 