AceShowbiz -

The ongoing custody drama between Britney Spears and ex-husband Kevin Federline is heating up. Los Angeles police were called to the singer's Beverly Hills home on Thursday night, January 3 after she refused to hand over sons Sean Preston and Jayden James to K-Fed's bodyguards as ordered by the court.

K-Fed's bodyguards, according to several news media, went to pick up Sean and Jayden at Britney's home after her scheduled visitation. She however refused to turn the kids over and so police were called for what was cited as "family custody dispute."

There were six police cars, an ambulance and a fire truck spotted outside the gates at Britney's home around 10:30 P.M., but none of the vehicles were flashing sirens. The showdown, as claimed by Perez Hilton, lasted for almost four hours.

K-Fed, in companion with his lawyer and Spears' law firm, showed up shortly thereafter and the boys were turned back to him just before 11:00 P.M. PT. The authorities at Spears' house, elsewhere, discovered that the singer was "under the influence of an unknown substance" and thus was taken to Cedars-Sinai Medical Center for mental evaluation.

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