The Sheriff's Department says it is investigating Mel Gibson over a possible domestic violence incident involving his ex-girlfriend earlier this year.

The agency said in a news release Thursday that it has opened a preliminary inquiry into the alleged attack.

Gibson is named as a potential suspect. His former girlfriend, Russian singer Oksana Grigorieva, is named as a possible victim.

The release states the alleged attack occurred Jan. 6.

A sheriff's spokesman was not immediately available to offer further details.

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A phone message left for Alan Nierob, Gibson's spokesman, was not immediately returned.

Gibson is no longer on probation for a 2006 drunken driving case, and his conviction has since been expunged.