Polygamist Warren Jeffs, who is behind bars for child rape, is under investigation for preaching to his cult members on Christmas day from behind prison bars, according to officials.

Jeffs, convicted of sexual assault of two girls, ages 12 and 14, who he claims were his “spiritual brides,” is serving a life sentence in a Texas prison and is now being investigated for possibly preaching to his cult members via telephone, which is a violation of prison rules.

"We have confirmed that Jeffs made two phone calls on Christmas Day to a relative," Texas Department of Criminal Justice spokesman Jason Clark told the LA Times. "At this point, we're investigating whether he may have circumvented policy and may have spoken to his congregation."

Fredrick Merril Jessop, a veteran bishop for the Fundamentalist Church of Jesus Christ of Latter Day Saints, was found guilty Monday of illegally marrying his 12-year-old daughter to convicted cult leader Warren Jeffs.

It took the West Texas jury about an hour and 20 minutes Monday to find Jessop, 75, guilty of the third-degree felony, which can be punished with two to 10 years in prison and $10,000 in fines.

"Fredrick Merril Jessop married a freckled, 12-year-old girl to a 50-year-old man," prosecutor Angela Goodwin told jurors in the trial regarding the illegal ceremony, which she said occurred July 27, 2006 at the Yearning For Zion Ranch near Eldorado, Texas.

In August, Jeffs was found guilty on two felony counts of child sexual assault, involving Jessop's 12-year-old daughter and another 15-year-old girl.

Warren Jeffs, the ailing polygamist cult leader who was convicted of child rape, was moved to a different hospital via helicopter on Tuesday, following his latest fasting stint that landed him in medical care over the weekend.

Jeffs, 50, was taken from a hospital in Tyler, Texas to a prison hospital in Galveston for treatment via helicopter.  He is now awake and responsive according to the Salt Lake Tribune.

Jeffs’ fasting and other health concerns were the reason behind his hospitalization apparently.  “He’s not on a hunger strike,” the prison spokeswoman Michelle Lynons insisted. “He doesn’t appear to be eating enough,” they conceded, but said Jeffs’ hospitalization was “because of the other medical issues, not related to his fast.”

Convicted child rapist Warren Jeffs is in critical condition after being rushed to a Texas hospital after falling ill while fasting in jail, RadarOnline.com can report.

The polygamist cult leader, and former head of the Fundamentalist Church of Jesus Christ of Latter Day Saints, is in prison serving a life sentence after being found guilty of sexually assaulting two young girls, ages 12 and 15, whom he claimed were his “spiritual wives.”

Jeffs is in the East Texas Medical Center in Tyler and the prison spokesman described his condition on Monday.  “Jeffs has not been eating/taking in fluids as he should,” the Salt Lake Tribune reported 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.”

Polygamist cult leader Warren Jeffs is sitting in prison serving his sentence of life plus 20 years for raping two underage girls, ages 12 and 15, who he claimed were his "spiritual wives."

The 55-year-old leader of the Fundamentalist Church of Jesus Christ of Latter Day Saints led his congregation with strictly conservative rules, from their clothing, to no alcohol to almost no exposure to the outside world, so it is shocking to see the photographs of him in modern clothes taken while he was on the run from the law.

PHOTOS: Warren Jeffs On The Run

Warren Jeffs has begun serving his life sentence behind bars, and in these shocking new photos,  the convicted rapist has had his head shaved for his prison stay.

Jeffs, 55, is the polygamist cult leader who was convicted of aggravated sexual assault of a 12-year-old girl and sexual assault of a 15-year-old girl, both of whom he claimed were his “spiritual wives.” The older girl gave birth to his child.

The Texas jury gave the leader of the Fundamentalist Church of Jesus Christ of the Latter Day Saints life plus 20 years sentences after a horrifying trial where multiple witnesses testified about the long term sexual abuse perpetrated by Jeffs.

A former polygamist wife has spoken of her joy at cult leader Warren Jeffs, 55, being found guilty on Thursday of sexually assaulting two young girls, ages 12 and 15.

Flora Jessop was married off to her older cousin when she was 16-years-old and said she suffered horrific sexual abuse from the time she was 13 before she finally escaped the cult.

Polygamist cult leader Warren Jeffs was found guilty of sexually assaulting two young girls, ages 12 and 15, by a Texas jury on Thursday.

Jeffs, 55, was found guilty of aggravated sexual assault against the 12-year-old girl and guilty of sexual assault of the 15-year-old girl.

The jury deliberated for three hours before reaching their verdict and the 10 women and 2 men did not look at Jeffs when the verdict was announced.