California officials are investigating a state prison inmate they suspect used a Facebook account to post messages to his mother and others from behind bars.

Fredrick Garner had access to a cell phone, which is forbidden in prison, and appears to have posted messages after prisoners were supposed to be asleep, said Department of Corrections and Rehabilitation spokeswoman Terry Thornton.

However, until investigators finish analyzing the phone they can't rule out the possibility that Garner's girlfriend posted the messages for him, which would be permissible, Thornton said.

Garner has served nearly 10 years of a 22-year Sacramento County sentence for voluntary manslaughter. He is being held in Corcoran State Prison, the same prison where cult killer Charles Manson was found with a cell phone in 2009.

Thornton said that while Garner's postings appear harmless, inmates have used cell phones to coordinate assaults and escapes. More than 9,000 cell phones were recovered in California prisons last year, up from 261 four years ago.

Possessing a cell phone violates prison rules, but is not illegal.

Former Gov. Arnold Schwarzenegger last year vetoed a bill that would have made it a misdemeanor to smuggle cell phones in prisons, saying the bill did too little to deter smuggling. State Sen. Alex Padilla, D-Los Angeles, has reintroduced that bill this year as SB25, along with a second bill, SB26, that would add penalties for inmates caught with the phones.

Investigators don't know how long Garner was posting to Facebook, Thornton said. His Facebook postings were first reported by CBS13 in Sacramento, which showed a Facebook profile photo of Garner and his girlfriend. The account, which included messages to Garner's mother, has since been taken down.

"Hi mom, love you bunches! lots of hugs and kisses 4 you. thank you mom4 everything," reads a Dec. 12 posting.

Guards found paper copies of Garner's Facebook postings in his cell last month, though Thornton said those could have been downloaded and mailed to him from outside prison.

"If they want to communicate with a third party and that party wants to post information, I don't know that there's anything we can do about that," Thornton said.

Garner, 40, has not been cited for any rules violations involving the cell phone or Facebook postings. He and two other inmates have been held in a disciplinary segregation unit since Dec. 17 on unrelated allegations that they instigated a fight in a prison exercise yard, Thornton said.