A Los Angeles police officer, who requested anonymity because he was not authorised to speak on the matter, said the 26-year-old pop star was being taken to get help but did not say where the ambulance was going.
On January 3, police were called to her Studio City home when she refused to return her two young sons, Sean Preston, 2, and Jayden James, 1, to ex-husband Kevin Federline, who has custody.
Officers had paramedics haul Spears to a hospital for undisclosed reasons. She was released after a day and a half in Cedars-Sinai Medical Centre.
Police also went to the home Monday night after someone reported a swarm of paparazzi trespassing in the singers gated community. When officers arrived, they didnt see anyone trespassing, police said, but citations were issued for several illegally parked cars.
Spears has been in a highly public downward spiral since filing for divorce from Federline in November 2006.
Her bizarre antics include shaving her head bald, attacking a car with an umbrella and bringing along a paparazzo pal on trips to a courthouse in her child custody case.