Britney Spears hit a perilous new low on Thursday night when authorities reportedly responded to a family-custody dispute at her house in Studio City, California. According to TMZ.com and other outlets, the singer refused to turn over her two children to ex-husband Kevin Federline, and authorities discovered her under the influence of an unidentified substance.

The Los Angeles Police Department was reportedly called to Spears' house after a person who has not been identified phoned authorities at 8 p.m. over a domestic disturbance. The call involved a "family custodial dispute that we are trying to resolve ... peacefully by court order," LAPD spokesman Officer Jason Lee told The Associated Press. She was due to have her sons, Sean Preston and Jayden James, until 7 p.m. that day. UsMagazine.com later reported that Federline's bodyguards had gone to pick up the children at Spears' house, but she refused to turn them over, despite a court order to do so. An unnamed source told People.com that Spears' court-appointed monitor called police after "[the monitor] had already put [Sean] Preston in the car when Britney locked herself in a room with Jayden." Spears had been with the children since noon, according to UsMagazine.com. Federline's attorney Mark Vincent Kaplan had also been at the residence, TMZ reports.

Police went to Spears' home 90 minutes later, as did ambulances, fire trucks and a police helicopter, according to TMZ. While there, authorities reportedly found Spears "under the influence of an unknown substance," TMZ reports. She was later taken out of her home on a gurney by paramedics and taken to a local hospital, where she was reportedly placed under medical evaluation. Paparazzi photos of the incident show Spears smiling broadly as she is being held down by paramedics; an unnamed source told Usmagazine.com that the singer went "completely psycho" as she was rushed to the hospital. "They had to strap her down like a mental patient and she was going between laughing and hysterics," the source said. According to multiple reports, the children are in the custody of Federline, who has temporary custody of the children because Spears has not obeyed court orders.

At press time, the singer reportedly was still hospitalized under observation, with an unnamed hospital source telling Usmagazine.com that she has been designated a "special needs" patient, meaning "they have either overdosed or tried to commit suicide. So we go stay with these patients and monitor them constantly. We watch them so they don't hurt themselves and watch the people who come visit them to make sure they don't pass anything to them." Britney's friend Sam Lufti was seen leaving the hospital at around 2:20 a.m. People.com reported that Spears will be held on a minimum 72-hour lock down for mental evaluation, according to the unnamed source. CNN reported that Spears' three-day lockdown is a result of a part of California's "5150" law, which allows health professionals to involuntarily admit someone for up to three days if they are believed to be a threat to themselves or others.

An unnamed source also told the magazine that the singer's sons were both released from Cedars-Sinai Medical Center shortly after 4 a.m. on Friday. They were driven away by one of Federline's bodyguards, who was pursued by the paparazzi as he left the area. Federline had reportedly returned to his Tarzana, California, home before the boys arrived.

Earlier in the day, Spears finally sat down for her [article id="1578975"]long-awaited deposition in her child-custody battle,[/article] although she cut the session short and was only questioned for 14 minutes. She had been scheduled to start her deposition at 9:45 a.m. but didn't leave her home until after 10 a.m., according to photos and video taken of her drive to her ex-husband's lawyer's offices in Century City, California. By the time Spears arrived, she was 90 minutes late, and proceedings didn't start until just after 11:30 a.m., according to Kaplan.

"I would've preferred it had gone on longer," Kaplan told reporters waiting outside the deposition. Kaplan was expected to ask the pop star, who he called "cooperative," about her alleged drug and alcohol use around her sons, as well as her driving habits and parenting techniques. Whether he got the answers he sought, he wouldn't say, except to offer, "You can imagine in 14 minutes there's not a lot of time to develop questions."

Spears lawyer Sorrell Trope, a partner at the law firm Trope and Trope -- which on Wednesday [article id="1578873"]asked to be withdrawn as her legal counsel[/article] -- told UsMagazine.com in reference to the Thursday night incident, "In a normal case when someone shows up with a certified court order saying the kids need to be somewhere else, the police see to it that the order is obeyed. But that is in a normal case."