Mel Gibson in domestic violence probe

Mel Gibson is being investigated in a possible domestic violence incident involving his ex-girlfriend, Los Angeles sheriff's officials said Thursday.

The Los Angeles County Sheriff's Department listed the actor-director as a potential suspect in the alleged attack in January on Russian singer Oksana Grigorieva at an undisclosed location in Malibu, Calif.

The two have been involved in a nasty custody dispute over their infant daughter — the subject of a confidential court case.

Sheriff's spokesman Steve Whitmore said detectives interviewed Grigorieva on Monday. She has been the only person interviewed so far.

Whitmore declined to disclose further details of the investigation or any potential evidence.

"We're in the process of verifying, verifying, verifying," Whitmore said. "All the allegations that have been put forth will be thoroughly investigated."

The allegations are being handled by the same sheriff's substation that handled Gibson's 2006 arrest on suspicion of drunken driving. The station in Agoura also covers Malibu, where Gibson lives.

The release states the incident occurred Jan. 6 and the investigation is in a preliminary stage.

The Academy Award winner completed his sentence for the drunken driving case and his conviction has been expunged.

The actor has not publicly discussed the breakup with Grigorieva, 40. They first revealed their relationship shortly after Gibson's wife, Robyn, filed for divorce in April 2009.

Whitmore said it may take a month to conclude the investigation.