Mel Gibson and his ex-girlfriend Oksana Grigorieva are already in the middle of a custody battle surrounding their eight-month-old daughter, Lucia.
And now police have stepped in after Oksana made allegations of an aggression on the part of her former lover.
A statement released on Thursday read: "An investigation of domestic violence was launched by Malibu/Lost Hills station detectives involving actor Mel Gibson and his former girlfriend Oksana Grigorieva.
"The detective in charge of the investigation is currently gathering information regarding the allegations. Due to the investigation being preliminary in nature, no other information is available at this time."
A spokesman for the Los Angeles Sheriff's Department says it could take up to a month to complete the case, at which time it will be handed over to the district attorney's office.