Woman Takes 2 Daughters at Knifepoint : Custody: The girls, placed in foster care by L.A. County, are abducted from a social worker.

A Los Angeles woman who abducted her two young daughters at knifepoint from a social worker was being sought Wednesday by authorities who said they fear for the children’s safety.

The woman, Ana Urbina, 37, told relatives about three weeks ago that she was going to kill herself and the two children, said Deputy Laurie Savage of the San Bernardino County Sheriff’s Department. “We’re obviously concerned about her mental condition and the safety of the children.”

Her daughters, Catherine, 3, and Anna, 5, were placed in foster care by the Los Angeles County Department of Children’s Services while she and her estranged husband tried to resolve a custody battle, Savage said. Ana Urbina had made arrangements Monday to visit the girls at a foster care facility in the nearby community of Grand Terrace, under the supervision of a social worker there, Savage said.

During the visit, Urbina bared a kitchen knife and, with the children in tow, forced the unidentified social worker to drive five miles to a bus stop at the border of San Bernardino and Loma Linda, Savage said.

At the bus stop, Urbina took the girls out of the car, released the social worker unharmed and fled on foot. The woman and the two girls have not been seen since, and there were no indications she has returned to her home near MacArthur Park, Savage said.

A warrant has been issued for her arrest on one count of kidnaping of the social worker and two counts of child abduction, Savage said.

“We’ve had five detectives working this case, and they haven’t come up with any leads,” she said. It was unclear why the social worker did not follow Urbina and the children after they got out of her car, Savage said.

The incident occurred at an office operated by Guadalupe Homes, a private, nonprofit foster care and treatment center licensed by the state Department of Social Services. A spokesman there was unable to give further details of the alleged kidnaping.