Rotting marijuana that Michael Jackson's family members mistook for heroin briefly caused detectives to look for further evidence of the illegal drug in the pop star's rented residence during the frenzied 48 hours after his death, according to sources close to the investigation.

Family members told coroner's officials that they found "tar heroin" in the Holmby Hills home's master bedroom. Only Jackson and his children had access to the room, according to court records unsealed Thursday. The discovery prompted authorities to obtain a search warrant for Jackson's house for heroin, hypodermic needles, cutting agents, scales, balloons, condoms, razor blades, buyer lists, and seller lists, among other items, documents show.

But within days, police had ruled out heroin as a factor in the singer's death, sources close to the investigation said. Lab tests showed that the purported heroin was actually moldy marijuana, sources said. And, according to court records, a lengthy police interview with Jackson's personal physician, Dr. Conrad Murray, placed another drug, the powerful anesthetic propofol, at the center of the investigation.