LOS ANGELES (AP) -- A district attorney's spokeswoman says Los Angeles police have presented a case regarding singer Chris Brown, but county prosecutors have asked for further investigation.

Spokeswoman Jane Robison did not release information on the nature of the case police presented to prosecutors Tuesday, and she says the district attorney's office will have no further comment pending the investigation.

Police booked Brown on Sunday for investigation of making a criminal threat after a woman accused him of assaulting her the night before the Grammy Awards.

The Los Angeles Times, citing unidentified law enforcement sources, has reported that the woman is pop superstar Rihanna, his longtime girlfriend.

Brown is free on $50,000 bail.