Detectives from the Los Angeles Police Department's "threat management" squad have opened a criminal investigation of actor Charlie Sheen, a police spokesman said on Wednesday.

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Police disclosed little else about the investigation, which the LAPD spokesman, officer Mike Lopez, said began with a complaint lodged against the actor on March 31.

Lopez declined to provide any information about the nature of the alleged victim or threat, but said investigators had obtained a search warrant in the case, and that as of Wednesday afternoon had yet to contact Sheen. 

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Unconfirmed reports from media outlets, including Variety and RadarOnline.com, referred to an audio tape they said was at the center of the investigation.

A lawyer for Sheen, best known for his starring role on the long-running hit CBS comedy "Two and a Half Men," could not immediately be reached for comment.

The police investigation marks the latest brush with the law for the 50-year-old actor, whose career has been overshadowed for years by his admittedly raucous lifestyle, substance abuse, stints in rehab and legal troubles.

Last November, Sheen acknowledged he had been diagnosed as HIV-positive four years earlier and was being extorted for more than $10 million to keep that information quiet.

He pleaded guilty in August 2010 to assaulting his then-wife, Brooke Mueller, during a Christmas Day argument in Aspen, Colorado, and was sentenced to 30 days in a drug and alcohol treatment center in California.

According to Mueller's account of the Aspen incident in a police report, Sheen had pinned her to their bed and put a knife to her throat. The couple later divorced.

In March 2011, a judge ordered their two sons removed from the actor's home after Mueller obtained a stay-away order against Sheen, claiming he had threatened her.