LOS ANGELES, California (CNN) - Singer Michael Jackson took more than 10 Xanax pills a night -- asking his employees to get the prescription anti-anxiety medication and sleep aid under their names and personally traveling to doctor's offices in other states to obtain them, said a confidential document from 2004 that CNN obtained Thursday.
The document from the Santa Barbara County Sheriff's Department contains confidential interviews conducted with two of Jackson's former security guards as officials prepared for Jackson's child molestation trial in 2005.
The singer was acquitted after the 14-week trial. But the information about the medication -- and the lengths Jackson went to get them -- add to a growing mountain of claims tying the insomniac singer to drugs in recent days.
Los Angeles Police Chief William Bratton said Thursday that detectives had spoken to a number of doctors who had treated Jackson over the years, and were looking into the singer's prescription drug history.
Doctors who did not cooperate with investigators received subpoenas, a source told CNN Thursday. If needed, authorities will issue more, the source said.
Jackson died on June 25. Authorities await toxicology reports from the coroner's office to determine the exact cause of death.
"And based on those, we will have an idea of what it is we are dealing (with): Are we dealing with a homicide, or are we dealing with an accidental overdose?" Bratton said.
The speculation that prescription drugs, particularly sedatives, could have played a role in Jackson's death keeps coming up with each new nugget of information -- and there have been many.
The Jackson family knows that the probe into his death might turn into a criminal case, a source close to the family told CNN on Thursday.
"The family is aware of a potential criminal prosecution," said the source, who did not want to be identified.
The amount of Xanax that Jackson alleged took surprised CNN Chief Medical Correspondent Sanjay Gupta.
In addiction cases, people develop a tolerance to drugs and have to take more and more pills, Gupta said.
"No matter how you cut it, this is an extremely high dosage of Xanax," Gupta said. "It is a huge red flag, even with the tolerance that I was talking about. This dosage is exceedingly high for any human being."
The 2004 document details a dark picture of Jackson's attempts to battle his sleeping disorder.
One security guard that sheriff's deputies interviewed said he expressed his concern about Jackson's use of 10-plus pills a night to another staffer.
The second staffer replied: "Jackson was doing better because he was down from 30 to 40 Xanax pills a night," according to the document.
One of the guards said he and three other employees would get prescriptions for Jackson under their names.
The second guard backed up the claim, saying he had picked up medicine for the singer that were in other people's names.
The document contains the names of five doctors -- in California, in New York and Florida. It was not immediately clear whether police had spoken to them as part of their investigation into Jackson's death.
After the doctor visits, Jackson would be "out of it and sedated," one guard said.
According to the sheriff's office document, the guard who provided the bulk of the information quit his job after Jackson "fell on his face" in a hotel room and hurt himself. The employee told Jackson he was not comfortable getting prescriptions for him and left, he later told investigators.
Several years later -- in 2006 -- Jackson was in Las Vegas trying to jump-start his career. Deal maker Jack Wishna, who was helping the singer land a long-running show in Vegas, told CNN the singer would appear "drugged up" and "incoherent" -- often so weak and emaciated he had to use a wheelchair.
The comeback shows were canceled because of Jackson's condition, Wishna said.
About that time, sister Janet Jackson was so worried about Jackson that she tried to stage an intervention with assistance from her other brothers, two sources close to the Jackson family told CNN on Wednesday.
Jackson reportedly ordered his security guards not to let the family members in. He also refused to take calls from his mother, Katherine, CNN has learned.
At the time, the Jackson family released a statement to People magazine denying the alleged intervention. But Janet Jackson was not among the signatories.
Along with the police investigation -- which is being aided by the state attorney general's office and the Drug Enforcement Administration -- the Los Angeles County coroner's office has drawn up a list of Jackson's doctors and is trying to talk to them to determine what drugs they may have prescribed him.
Among them are Dr. Arnold Klein, Jackson's dermatologist, and Dr. Conrad Murray, his cardiologist.
Klein told CNN on Wednesday that Jackson was addicted to drugs at one point, but had kicked the habit.
Murray -- who has been interviewed by police -- has repeatedly said he will withhold comment until the coroner's tests are back.
Among others who have indicated that Jackson may have been using dangerous prescription medication are a nutritionist -- Cherilyn Lee -- who said Jackson pleaded for the powerful sedative Diprivan despite being told of its harmful effects.
Sources close to Jackson told CNN that the insomniac singer traveled with an anesthesiologist who would "take him down" at night and "bring him back up" during a world tour in the mid-'90s.
Another source involved with the probe told CNN that investigators found numerous bottles of prescription drugs in the singer's $100,000-a-month rented mansion in Holmby Hills.
The Associated Press and the Los Angeles Times, citing unnamed sources, said police found Diprivan.
Diprivan is administered intravenously and is known by its generic name, Propofol.
Bratton, the police chief, did not elaborate on what was discovered.
"At the time of the death, with search warrants, we were able to seize a number of items from the residence where the death occurred, and those will assist in the investigation," he said.
Meanwhile, Jackson's family has been told by state officials that it may be possible to bury the singer at Neverland Ranch -- if the county grants the green light.
Officials with Santa Barbara County, where the ranch is, said Thursday that they had not been approached.
A lawyer from the Jackson family contacted state officials recently about possibly burying Jackson at the ranch, which was his home for almost two decades, said Amanda Fulkerson of California's State and Consumer Services Agency.
Burying someone in private land in California is a two-step process.
First, a certificate of authority is needed from the state Cemetery and Funeral Bureau -- easily obtainable by filling out a two-page application and paying $400.
Next, the family needs approval from the county.
No one from the Jackson camp had contacted county authorities, said county spokesman William Boyer.
"We have had no formal application either from the Jackson family or from the property owner," said Boyer, communications director for the county. "At that point, we would review the application and make a determination."
The county has never been approached before about burial on private land, Boyer said.
California has had burials outside cemeteries, most notably that of former U.S. President Ronald Reagan at his presidential library in Ventura County's Simi Valley.
Jackson's brother Jermaine has said he'd like to see the singer buried at the ranch. But his father, Joe Jackson, has ruled out the site.
The rest of the family has not publicly indicated where the singer's final resting place will be.
Jackson purchased Neverland Ranch -- named for the fictional world in J.M. Barrie's "Peter Pan" -- in 1987 and filled it with animals and amusement rides.
Billionaire Tom Barrack Jr. gained control of the ranch through his company last year as part of a process to alleviate the singer's debts, thought to be in the millions.