Pop star Michael Jackson died from a lethal dose of the powerful anesthetic propofol given in a cocktail of drugs, leading authorities to suspect his doctor of manslaughter, court documents showed on Monday.

The “Thriller” singer suffered cardiac arrest and died on 25 June at age 50. Since then, an investigation by state and federal agencies have focused on Conrad Murray, Jackson’s personal doctor who was at his bedside the day he died.

The findings, contained in a warrant to search Murray’s home and offices, paint a picture of an insomniac pop star who could not sleep without heavy medication. Jackson sought out propofol — routinely used to sedate patients and anesthetize them before surgeries such as a colonoscopy — and called it his “milk.”

“The Los Angeles chief medical examiner-coroner, Dr (Lakshmanan) Sathyavagiswaran, indicated that he had reviewed the preliminary toxicology results and his preliminary assessment of Jackson’s cause of death was due to lethal levels of propofol (diprivan),” according to a warrant to search Murray’s offices issued by California.

The document was unsealed and released by the Harris County District Clerk in Houston, where Murray has an office. US agents raided the office on 22 July.

In an affidavit seeking the warrant, Houston police officer EG Chance said US agents had gathered “items constituting evidence of the offense of manslaughter that tend to show that Dr Conrad Murray committed the said criminal offense.”

Murray’s attorney, Ed Chernoff, was not available to comment.

In a statement, a representative said Jackson’s family has “full confidence in the legal process, and commends the ongoing efforts of the LA County Coroner, the LA District Attorney and the LA Police Department.”

Murray, who was with Jackson on 25 June administering drugs to ease the pop star to sleep, gave him a range of medication including a 25-milligram dose of propofol via an intravenous drip, the state search warrant said.

Jackson was “very familiar” with propofol and referred to it as his “milk” because of its milky appearance, the warrant said. Murray, who had been treating Jackson for about six weeks leading up to his death, was worried that Jackson was addicted to propofol. Murray was trying to wean him off the drug by giving him smaller doses, it said.

Jason Hymes, an assistant clinical professor at the University of Southern California who is not associated with the case, said the drug was a true anesthetic. “You administer it to somebody and then operate on them ... This concept of giving somebody a general anesthetic for sleep disturbance strikes me as just bizarre and astoundingly inappropriate.”

In the early hours of 25 June, Murray also gave Jackson doses of anti-anxiety medications Valium and Ativan and sedative Versed, the filing said.

Jackson went to sleep after Murray gave him the propofol, and Murray stayed by his side for about 10 minutes, then left “to go to the restroom and relieve himself,” the search warrant said.

Murray was out of Jackson’s room for about 2 minutes and when he returned, Jackson was no longer breathing, the warrant said.