Rihanna assists police in Chris Brown case

R&B; star Rihanna is cooperating with investigators building a domestic violence case against her boyfriend, the singer Chris Brown, a police source said Monday.

The source said the 20-year-old performer, whose full name is Robyn Rihanna Fenty, was providing “ongoing” cooperation to detectives who booked Brown on Sunday on suspicion of making criminal threats against her.

An early morning altercation with Brown after a pre-Grammy Awards party left Rihanna with bruises and a scratch on her face, according to police sources. She was treated at a “major medical facility,” a police source said.

Brown, 19, has a double-platinum record and dance moves often compared to Michael Jackson’s. He fled before officers arrived, police said.

He remained free on $50,000 bail, but neither he nor his attorney would speak about allegations that rocked the Grammys ceremony. Brown and Rihanna were both nominated; neither attended the ceremony.

The fight occurred after midnight on a quiet block in Hancock Park, where Brown had stopped a rented Lamborghini he was driving. According to police, several people saw or heard a loud, violent confrontation. The luxury car was impounded because the alleged assault may have begun in the vehicle, a police source said.

Commercial fallout began Monday, when the makers of Doublemint gum suspended an endorsement deal. A commercial in which Brown dances and sings a version of the gum’s jingle aired during the Grammys. By then, many viewers knew of the accusations against him.

“Wrigley is concerned by the serious allegations made against Chris Brown. We believe Mr. Brown should be afforded the same due process as any citizen. However, we have made the decision to suspend the current advertising featuring Brown and any related marketing communications until the matter is resolved,” the Wm. Wrigley Jr. Co. said in a statement.

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richard.winton@latimes.com

harriet.ryan@latimes.com

Times staff writer Andrew Blankstein contributed to this report.