Sheriff's detectives in Los Angeles are checking extortion allegations against Mel Gibson's ex-girlfriend.

Sheriff's spokesman Steve Whitmore says the agency is looking into whether Russian singer Oksana Grigorieva may have tried to extort the Academy Award-winner. He declined to offer any other details on the inquiry.

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Detectives earlier this month interviewed Grigorieva after she claimed Gibson abused her during an incident in January.

A spokesman for Grigorieva declined comment Wednesday.

Gibson and Grigorieva are locked in a bitter custody dispute over their infant daughter.

No arrests have been made, and neither has been charged with any crimes.