Updated

The death row inmate convicted of kidnapping and murdering 12-year-old Polly Klaas more than a decade ago overdosed on opiates in his prison cell but was revived, prison officials said.

Richard Allen Davis, 52, was found unconscious Sunday in his San Quentin State Prison cell and was treated at the prison infirmary and a local hospital, prison spokesman Vernell Crittendon said Monday.

Davis was returned to his cell hours after the incident and was "doing fine" Monday, Crittendon said.

It was not clear whether the overdose was accidental or a suicide attempt, and officials had not determined where Davis got the drugs, though they suspected a visitor or another inmate smuggled them into the prison.

Davis was already a repeat offender when he broke into the Petaluma girl's home in 1993 and kidnapped, molested and killed her.

The case became national news and efforts by Klaas' parents to prevent similar tragedies led to the creation of the state's three-strikes law.

California voters approved the law in 1994 requiring a sentence of 25 years to life for criminals with two prior convictions for serious or violent felonies who are then convicted of a third felony.

Davis' crime and his role in the creation of the strict sentencing law made him a target for other inmates, and he has been assaulted and spat upon by other inmates at least three times, Crittendon said.