Britney Spears in hospital, may lose child visits (Reuters)

LOS ANGELES (Reuters) - Lawyers for Kevin Federline, ex-husband of pop star Britney Spears, went to court on Friday seeking to strip the troubled singer of visitation rights to their sons hours after she was hospitalized following a fit of hysterics.

In the latest twist in Spears year-long personal meltdown, police and ambulances were called to her Los Angeles house on Thursday night, police said.

Television reports showed Spears, 26, being taken out of her home on a gurney early on Friday and driven to Cedars-Sinai Medical Center in an ambulance.

Los Angeles police spokesman Jason Lee said Spears was under the influence of an unknown substance and was being detained and evaluated in the hospital. Lee said no injuries were reported.

Lawyers for Federline met in private with the judge handling the child custody dispute on Friday morning and were due back in court in the afternoon to discuss the Spears incident.

According to celebrity news Web sites, Spears locked herself in a room with one of her children and went into hysterics when aides of Federline arrived to pick up sons Sean Preston, 2 and Jayden James, 1, from a court-authorized visit.

TMZ.com said Spears was expected to remain hospitalized under evaluation for her mental state for at least 48 hours.

Us magazine, citing a hospital source, said Spears had been designated a "special needs" patient and was under constant watch. Another source told the magazine that in the ambulance Spears had to be restrained like a mental patient and that she "was going between laughing and hysterics."

Cedars-Sinai declined to comment, citing patient confidentiality.

Spears lost primary custody of the boys in October to Federline after her life spun out of control following their divorce, her stints in rehab, a bizarre head-shaving episode and reports of drinking and drug use.

She is currently undergoing court-ordered random drug and alcohol tests and has court-monitored visits with her children three times a week.

Spears, who became a teen pop phenomenon nine years ago, has rarely been out of the news since her split with Federline in November 2006 after two years of marriage.

She made her musical comeback in October with a new single, "Gimme More," and an album, "Blackout," that played strongly on radio and digital download charts and briefly hit No. 2 on the U.S. pop album charts.

(Reporting by Jill Serjeant; Editing by Bob Tourtellotte and Xavier Briand)