R&B singer Chris Brown and Rihanna both canceled their performances at Sunday's (February 8) Grammy Awards, after reportedly being involved in an domestic dispute and possible altercation the day of the show.

Brown turned himself into the Los Angeles Police Department for questioning for an allegedly assault on a female early Sunday morning. According to the Los Angeles Times, that female was none other than his girlfriend Rihanna, although the LAPD did not name her.

Details about the incident are sketchy. But the paper reports that around 12:30 a.m. Sunday, Brown and the unnamed woman were involved in an argument in a rented Lamborghini around Hancock Park. Brown stopped the car, the couple got out, and the argument escalated.

A witness called 911. But when police had arrived, Brown had already left the scene. The woman identified Brown as her assailant.

Authorities are holding further details about her injuries and whether or not she needed treatment. Sources, however, told the LA Times that the woman was Rihanna (real name: Robyn Rihanna Fenty).

Brown was reportedly booked on a making criminal threats charge, and police said he remained under investigation for felony charges of domestic violence.

"The exact charge was criminal threats and it is going to be investigated as a criminal threats investigation," said Police Sgt. Bridgett Pickett. "There may be domestic violence charges added later, but that will be up to the district attorney's office."

The singer posted $50,000 bail, and was released around 9 p.m.

Rihanna's publicist issued a statement late Sunday, saying she was "well" and thank fans for their support.

Both were scheduled to attend and perform at Sunday's Grammy Awards, but neither attended.