The Britney Spears circus took a sad turn Thursday night as police, firefighters and ambulances were called to Britney’s Beverly Hills home after she refused to give her children back to ex-husband Kevin Federline.

Another ambulance, more fire trucks and several additional police cars have just rolled up to Britney’s house. One person on the ground described the situation to us as “scary.”

We’ve learned Spears has refused to turn her two sons back over to their daddy tonight, as ordered by the court. LAPD tells us they’ve been called to the home to deal with the family custody dispute.

Spears, heavily under the influence of either drugs or alcohol, finally gave the kids back over to K-Fed.

TMZ has learned Sean Preston and Jayden James were turned back over K-Fed tonight just before 11:00 PM PT.

More to Come…..

UPDATE: Britney Spears in Psych Ward Lockdown

Don’t forget to check out Top 35 Britney Spears Moments of 2007