Oksana Grigorieva and Mel Gibson Oksana Grigorieva and Mel Gibson

The Los Angeles Sheriff's Department is investigating Mel Gibson's extortion claims against ex-girlfriend Oksana Grigorieva, a department spokesman told TVGuide.com.

Spokesman Steve Whitmore confirmed an investigation into the Russian singer is under way, but he declined to offer any additional details.

Gibson's claims are related to the purported audio of Gibson yelling at and threatening Grigorieva that have recently leaked online. Gibson claims Grigorieva demanded payment and threatened to leak the audio otherwise.

Woman believed to be Mel Gibson's ex-girlfriend: You hit our baby while she was in my hands

Six recordings containing threats and racial slurs have been released thus far. Two weeks ago, the Oscar-winning director of Braveheart was dropped by his longtime agency, William Morris Endeavor, after an audio clip believed to be Gibson criticizing Grigorieva's choice of dress first leaked.Detectives interviewed Grigorieva earlier this month on her claims that Gibson abused her in January. She claims that Gibson punched her in the face multiple times on Jan. 6, breaking a tooth and causing a concussion. She filed a restraining order against him last week. The two are also embroiled in a bitter custody suit for their 8-month-old daughter.No arrests have been made and no charges have been filed in either case.Meanwhile, California Gov.

Arnold Schwarzenegger compared Mel Gibson on Wednesday to the Gulf of Mexico oil leak, telling utility commissioners in Sacramento that while BP appears to have contained its well, "no one has figured out how to contain Mel Gibson."

The Associated Press reported that Schwarzenegger also told them to turn off their cell phones "because we are expecting a call from him."

Gibson spokesman Alan Nierob told the AP he's happy to hear that Schwarzenegger is maintaining a sense of humor, adding, "He's obviously paving the way for a return to showbiz."