NEW YORK — Two-year-old twins from the Philippines born with the tops of their heads fused together were "strong and stable" after being separated in a marathon operation that stretched into early Thursday.

Surgeons, nurses and technicians applauded in the operating room after Carl and Clarence Aguirre were surgically separated at 10:32 p.m. Wednesday, said Steve Osborne, a spokesman for the Children's Hospital at Montefiore Medical Center.

The operation was completed around 3:15 a.m. Thursday, more than 17 hours after it began, Osborne said. Dr. David Staffenberg, the boys' plastic surgeon, said the boys were "strong and stable."

Several hours after the operation, the boys remained sedated and unconscious in the pediatric intensive care unit, with "vital signs fine, no apparent problems," Osborne said.

Staffenberg delivered the news of the separation to the twins' mother, Arlene Aguirre, in a private waiting area. He got on his knees, took Aguirre's hands and said, "You're now the mother of two boys," said hospital spokeswoman Pamela Adkins.

Aguirre burst into tears, she said.

Doctors teased apart abutting portions of the boys' brains after completing an incision around their skull, and the twins' head-to-head operating tables were then slightly pulled apart, said Osborne.

Reconstruction of the boys' skulls, a major project, is to be left for later.

The separation was the culmination of a gradual surgical approach that lasted 10 months, a departure from the more common marathon operations that have separated other conjoined twins.

It is likely to be months before the twins' conditions can be fully assessed, their doctors said. In the past, separation was considered a success if both twins simply survived. But Montefiore's goal for the Aguirre boys, who have never been able to sit up, stand straight or look at each other's face, was "viable, independent lives."

Over four major surgeries since October, the boys' separate-but-touching brains were gently pushed apart and the tangle of blood vessels they shared were cut and divided.

Between surgeries, the boys were given time to heal and to adapt to their rerouted circulation systems. Originally, veins near Clarence's brain were doing much of the circulation work for both boys, but scans showed dormant veins on Carl's side had "plumped up" and begun working in response to the surgery, lead surgeon Dr. James Goodrich said last week.

Arlene Aguirre and her mother, Evelyn Aguirre, were at the hospital throughout the operation, getting occasional updates from the doctors.

They had sent the feisty dark-haired boys into the operating room with tearful kisses at about 7:30 a.m. Arlene Aguirre placed a small figure of the Virgin Mary on her sons' gurney, and it stayed with them, on an instrument cart, through the surgery.

The doctors, as well as Montefiore and Blythedale Children's Hospital in Valhalla, where the twins have been living between surgeries and receiving physical therapy, have donated their services.

Two other little boys who were once joined at the head, Mohamed and Ahmed Ibrahim, celebrated their third birthday in June. The Egyptian twins were separated in October during a 34-hour operation in Dallas. They remain in Dallas with their parents while they await surgery to reconstruct part of their skulls.