Polygamous sect leader Warren Jeffs is in a coma and may not survive, a source close to Jeffs told ABC News.

Jeffs, 55, was taken to the East Texas Medical Center in Tyler on Sunday night in critical condition, He had been fasting for the past three days and became so weak doctors at the Texas prison where he is serving a life sentence induced a coma, according to the source.

Jeffs has not been eating/taking in fluids as he should, Texas prison spokesman Jason Clark said in a statement. He indicated he was not on a hunger strike but fasting. The inmate also has other medical conditions that have risen to the level of needing hospitalization.

Clark said he couldn't provide more information on the other medical conditions.

Earlier this month, the leader of the Fundamentalist Church of Jesus Christ of the Latter Day Saints, a polygamist sect of Mormonism, was convicted of sexually assaulting two underage girls -- members of his sect whom he claimed were his brides from celestial marriages. In October, Jeffs is scheduled to go on trial a second time to face charges of first-degree bigamy. A conviction could be punishable by up to 99 years or life in prison and include up to a $10,000 fine.

Extensive media coverage surrounding the case prompted prison officials last Tuesday to move Jeffs to a solitary cell at the Powledge Unit in Palestine, Texas. The East Texas Medical Facility in Tyler is the nearest major medical center to the Powledge Unit.

Michelle Lyons, spokeswoman for the Texas Department of Criminal Justice told ABC News, Jeffs is in critical but stable condition, but added, I cannot confirm that he is in a coma.

Federal health privacy policies prohibit prison officials from releasing specific information about Jeffs' medical conditions.

He did indicate to staff that he was fasting, said Lyons, but he is currently being treated for other medical ailments and conditions.

Jeffs is serving a life prison sentence with no chance of parole for 45 years. He must serve at least 35 years of a life sentence on one of the child-sex charges, and at least 10 years on the other charges.