In a delicate, high-risk procedure that lasted 22 hours, surgeons separated 1-year-old Guatemalan twins who were joined at the head Tuesday morning, and doctors were optimistic for their recovery even though one of the girls required nearly five more hours of surgery.

Maria Teresa Quiej Alvarez and her sister, Maria de Jesus, were in critical but stable condition at the University of California, Los Angeles Medical Center. They were expected to remain sedated and using breathing tubes for days.

"I'm absolutely positive they will do OK. I'm absolutely positive if you go and visit them in five years they will be leading a normal life," said Dr. Jorge Lazareff, the lead neurosurgeon.

The doctors' sense was that the girls fared well, but it remained to be determined whether they suffered any brain damage, said Dr. John Frazee, a neurosurgeon.

"We just don't know neurologically. They're moving, which is a good sign. There's no way of knowing what the state of affairs is for another week," Frazee said.

There was no word from the parents, Wenceslao Quiej Lopez and Alba Leticia Alvarez. The mother spent eight days in labor at home in the town of Santo Domingo, Suchitepequez, before delivering the twins in a hospital by C-section.

Lazareff said that after the separation surgery Alvaraz said: "It's in the hands of God. It's God's will."

The initial news of the completed separation was blunted for much of the day after Maria Teresa was returned to surgery at 9:17 a.m. because of a buildup of blood on her brain, Lazareff said.

That operation took longer than expected, but nearly five hours later she was out of surgery again and back in the pediatric intensive care unit. The extra surgery was not expected to have any effect on Maria Teresa's long-term prognosis, Lazareff said.

The girls' weary doctors spoke glowingly of the surgical teamwork during a late afternoon news conference. Lazareff said he barely remembered the moment of separation because of the surgical teams' focus on a planned series of steps.

Although a medical center official had said there was cheering after the separation, Dr. Henry Kawamoto, a plastic and reconstructive surgeon, said there was no celebration at that moment.

"The separation occured and we just went on to the next step," he said. "... This is an operation that was planned well, executed extremely well, I think, and it was just the next step."

The surgery began at 8 a.m. Monday and the separation occurred about 1 a.m. Tuesday. The operation was completed at 5:40 a.m.

In Guatemala, Juliana Hernandez, the twins' 85-year-old great-grandmother, told local media that she wished she could hold the girls.

"I haven't seen them in a long time. I've just seen the papers and TV images of them, but at this moment I would love to have them here and hug them," Hernandez said.

The twins' relatives live in the village of Belen, about 125 miles south of Guatemala City. The 500 residents went to Mass Monday night to pray for the girls, local reporter Fredy Rodas told The Associated Press.

"We prayed a lot asking God to guide the doctors' hands during the surgery," said the twins' grandmother, Loyda de Jesus Lopez.

The girls, born in rural Guatemala, were attached at the top of the skull and faced opposite directions. While the two shared bone and blood vessels, they had separate brains. Cases like theirs occur in fewer than one in 2.5 million live births.

The riskiest part of the surgery was the separation of the veins that connected the girls' heads.

Surgeons at UCLA's Mattel Children's Hospital had to separate the individual blood vessels the two shared and decide which belonged to each child. Rerouting the flow of blood to and from the brain of each child put both at risk for stroke, said UCLA neurosurgeon Dr. Itzhak Fried.

That was followed by plastic surgery to extend the scalp of each child to cover the portion of exposed brain where they had been attached.

Kawamoto likened the procedure to the stretching of a peel over the exposed half of an orange that has been cut in two.

The two still face follow-up surgeries to reconstruct their skulls, but that may not happen until they are perhaps 6 years old.

"Right now their hair-do isn't much better than some of the undergrad students at UCLA," Kawamoto joked. "In the future we will be able to stretch the skin that we transplanted to give them a more normal appearance to their scalp and also bone-graft the areas that are deficient. But you have to understand, the goal this time was to get them separated and get it done safely."

Physicians around the world have performed cranial separations only five times in the past decade. Not all twins have survived.

Healing the Children, a nonprofit group, arranged to bring the sisters from Guatemala to Los Angeles for the $1.5 million operation. The UCLA doctors donated their services but hospitalization costs remained to be covered.

The girls' parents gave them kisses before the operation began, said UCLA spokeswoman Roxanne Moster.

"The girls were smiling a lot and were very playful," she said.

The Associated Press contributed to this report.