LOS ANGELES, California (CNN) — The person at Michael Jackson’s home who called 911 Thursday told the operator the singer wasn’t breathing and wasn’t conscious, according to a recording of phone call released Friday.”I need an ambulance,” the person told the 911 operator.

Police spoke with Jackson’s doctor on Thursday but have been unable to reach him Friday for further questioning, the Los Angeles Police Department said.A car the doctor was using was towed from Jackson’s home Thursday and impounded, authorities said.

The car may contain “medications pertinent to the investigation” into Jackson’s death, said detective Agustin Villanueva of the Los Angeles Police Department.Police did not release the doctor’s name.