Kiefer Sutherland, Brooke Shields

New York police are investigating a report that Kiefer Sutherland head-butted a fashion designer in an argument concerning Brooke Shields.

The 24 star tried to be a hero after the designer, Jack McCollough, knocked into Shields at a bar, New York's Daily News reported Wednesday.  

A police source told the newspaper that Sutherland had demanded the designer apologize to Shields before he head-butted him. Reps for Shields tell TMZ that McCollough "did nothing inappropriate. It's not clear what caused Kiefer to do what he did."

The designer was not believed to have suffered a broken nose or to have required hospitalization, a police source told TVGuide.com.

It's too soon to say if the police investigation could affect the filming of 24's eighth season, which a Fox rep said is set to begin production in New York later this spring. Sutherland's past run-ins with the law have not affected the show. After pleading no contest to a misdemeanor drunken-driving charge in 2007, he served 48 days in jail during the show's break from filming because of the writers' strike in early 2008.

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