Mel Gibson, Oksana Grigorieva

Mel Gibson could be in hot water again.

Just one week after Gibson's slur-filled rant against former girlfriend Oksana Grigorieva surfaced online, the actor is being investigated by Los Angeles County Sheriff's Department for a possible domestic violence incident between the pair, the Sheriff's department tells TVGuide.com.

"There have been allegations brought forth by his former girlfriend," said spokesman Steve Whitmore. "We interviewed the alleged victim on Monday, which officially launched our investigation."

Gibson and Grigorieva call it quits

The alleged incident took place on Jan. 6 of this year, but was not brought to the attention of the Sheriff's department until Monday. The investigation is in preliminary stages, according to Whitmore, and may take up to a month before they hand any evidence over to the District Attorney's office.

Whitmore declined to discuss any possible evidence relating to the case.

Gibson, 54, and Grigorieva, 40, are currently in a custody battle for daughter Lucia, whom they welcomed in October.

Gibson's camp did not immediately respond to TVGuide.com's request for comment.