Conjoined 10-month-old twin girls separated by a Chilean medical team are in critical condition after the surgery, and one is close to death, hospital officials said Friday.

"Their condition is grave, but it is very important that we point out that their recovery has not been equal," said Osvaldo Artaza, director of the Hospital Luis Calvo Mackenna where the twins were separated in a grueling operation that began Tuesday.

Maria Jose, who is smaller than her twin Maria Paz, is in "serious and delicate" condition following an arrhythmia episode Thursday that required resuscitation efforts, Artaza said. This places Maria Jose at a much greater risk of death, he added.

Maria Paz is faring somewhat better after the 20-hour operation which separated the two girls who had been joined at the chest and pelvis.

In all, some 100 professionals working in rotating teams of 24 worked on the children.

"The medical team expected a difficult first few hours after surgery and their recovery has been turbulent for both girls," said Artaza.

The operation involved separating the thorax, liver, and and then reconstruction of their organs and surrounding tissue. An earlier procedure two months earlier separated a leg they shared.

The girls are the daughters of a truck driver and a housewife from the southern town of Loncoche.

Jaime Manalich, who visited the twins on Wednesday, said the Chilean government is paying for the procedure, which hospital officials said would cost more than $200,000.

In 1993 two conjoined twin boys were separated successfully in the same in an operation that lasted more than 10 hours.