Sonoma County sheriff's detectives are investigating the death of an inmate who died early Thursday, jail officials said.

William Jackson, 59, of Petaluma had been convicted of drunken driving. He began serving a 120-day sentence on March 8, said Assistant Sheriff Linda Suvoy.

He was a minimum security inmate being housed in the North County jail facility.

Jackson had a previously diagnosed medical condition and was being treated for it, Suvoy said.

At about 6:45 a.m. Thursday other inmates in the dorm where he was housed reported that he was in medical distress. The inmates called for help and medical staff tried to resuscitate him, officials said.

He was taken to nearby Kaiser Medical Center and was pronounced dead. By 6:45 a.m. inmates typically already have had breakfast, Suvoy said.

An investigation by sheriff's detectives is standard procedure in an inmate death. It will include interviews with inmates sharing the dormitory with Jackson and a review of his health history, Suvoy said.

There was no initial evidence suggesting his death was related to anything other than the medical condition, Suvoy said.