Mel Gibson Focus of Domestic Inquiry

July 8, 2010— -- The Los Angeles Sheriff's Department is investigating Mel Gibson for a possible domestic violence incident involving his ex-girlfriend.

According to a department press release, Malibu detectives have opened a preliminary inquiry into the alleged attack, which took place Jan. 6, naming the Oscar-winning actor and director as a potential suspect and his former girlfriend, Russian singer Oksana Grigorieva, as a possible victim.

Mel Gibson's attorney, Stephen Kolodny, declined to comment, and his rep did not return phone calls immediately.

Gibson, 54, and Grigorieva, 40, are battling in court over their 8-month-old daughter, Lucia. The couple split up in April after they'd dated for more than a year. Two weeks ago, she filed for a restraining order against Gibson, claiming that he hit her at his Malibu home in January while arguing in front of their daughter. Sources close to the Russian-born singer claim that Gibson punched her in the face and broke her teeth.

According to Radaronline, Grigorieva has photos that show her bloodied and bruised after the alleged confrontation with Gibson. In published transcript excerpts from a tape recording of the incident, the website said it obtained, Radaronline claims a teary Grigorieva asked Gibson: "What kind of a man is that who would hit a woman when she is holding a child in her hands, hitting her twice in the face?"

On the tape, Gibson reportedly responds: "You know what -- you f**king deserved it."

Radaronline said Gibson's lawyer emphatically denied that he was violent toward Grigorieva.

A day after Grigorieva filed for the restraining order, Gibson filed for his own restraining order. A judge upheld their recent custody agreement, which gives him overnight and unrestricted visitation rights.

"Oksana's deceitful conduct in trying to terminate Mel's access to his daughter continues," Gibson's lawyer told TMZ.com last week. "Making sensational allegations is not the way to resolve this."

Last week, Gibson was under fire for reportedly using a racial slur during an argument with his former girlfriend.

Last Thursday, Radaronline.com published transcript excerpts the site said came from an audiotape of Gibson telling his ex, Oksana Grigorieva, with whom he's battling in court over custody of their infant daughter, that the way she is dressed made her look like a "pig in heat.

"If you get raped by a pack of n***ers, it will be your fault," Gibson reportedly shouted at Grigorieva, using a deeply offensive expression for African-Americans.

Radar claims to have heard the tape, which it says Grigorieva recorded when her relationship with Gibson was unraveling. The tape reportedly also includes Gibson calling Grigorieva a whore, and other profane names offensive to women, and threatening to burn down her house.

Grigorieva's attorney Marci Levine told ABCNews.com that it was not her client's "desire that the tape be released." She declined to comment further, citing the legal proceedings as confidential.

Gibson, however, appears to be his own worst enemy. Here's a roundup of some of his past comments that have gotten him into hot water: