Washington, Sept 8. (AP): Surgeons successfully separated 4-month-old conjoined twin boys, the lead surgeon declaring, "They are two separate individuals."

"Both are doing well," said the surgeon, Robert Keating. "All of the vital signs are doing well."

The boys' parents, Ryan Shaw, 28, and Angie Benzschawel, 25, said they were emotionally drained and relieved.

"It's been the longest day - but it's been the second-greatest day of our lives, obviously the birth was the first one," Shaw told reporters shortly after midnight. "Now, having two individual children that we can pick up at any given time, is going to be great."

The separation of Mateo Asher Shaw and McHale Twain Shaw took place about 12 1/2 hours after the first incision on Wednesday morning. Plastic surgeons then closed the surgical wounds of the boys late last night.

"It feels like we've been here for weeks," Benzschawel said of the hours spent waiting for news on her sons.

"We are very happy with the results," Shaw said. "We've been told that everything went as best as can be."

Both boys were listed early on Thursday morning in a critical, but stable condition.

Keating said it will be days or weeks before their recovery can be gauged.

Earlier in the day, the surgeons successfully separated the twins' spinal cords but kept their shared tailbone intact temporarily because of the stability it provided to surgeons as they repositioned the boys.

Following that, surgeons had to separate the boys' muscle, tissue and gastrointestinal systems.