A former fugitive on the FBI's Most Wanted list, Jeffs was arrested in August 2006 during a traffic stop near Las Vegas. While in a southern Utah jail awaiting trial, he suffered from depression, dropped as much as 30 pounds and was hospitalized after an attempted suicide in January 2007.
Jeffs is the head of the Utah-based Fundamentalist Church of Jesus Christ of Latter Day Saints. He is jailed awaiting trial on charges related to alleged underage marriages involving sect girls.
Mohave County sheriff's spokeswoman Trish Carter said force feeding of Jeffs started Friday at the Kingman, Arizona, jail after it was found he was not eating. Jeffs subsequently started eating on his own again and continued doing so until Monday night, she said.
But on Tuesday, Jeffs again refused to eat and is now being force-fed via a tube down his throat that delivers liquid nutrition, Carter said.
"Mr. Jeffs is closely being watched 24 hours a day," a statement from Carter said.
In a letter filed with the Mohave Superior Court on Friday, the jail's medical director said Jeffs had been refusing food and was no longer urinating. Medical Director Kirsten Mortenson said Jeffs' vital signs were worsening and he was suffering peripheral edema - the swelling of extremities like hands, feet and legs - brought on by "protein/calorie malnutrition."
"This deterioration will continue to accelerate and become harder to reverse the longer it persists," Mortenson wrote in a letter to Judge Steven F. Conn. "His death could be imminent without immediate medical intervention."
Contacted by cellphone Tuesday by The Associated Press, Mortenson said federal privacy laws prevented her from making any comment.
"I can't even tell you if I've seen him," she said.
Jeffs was moved to Kingman from the Utah State Prison in February 2008. In September 2007, a Utah jury convicted Jeffs of two counts of rape as an accomplice for his role in the 2001 marriage of an underage follower to her husband. He was sentenced to two consecutive prison terms of five years to life.
On Tuesday, Jeffs' Tucson, Arizona, attorney Michael Piccarreta said he did not know the status of his client's medical condition, but that the situation was not unusual.
"Mr. Jeffs is a deeply religious man and sometimes engages in lengthy religious practices while in jail. When he does, he declines food and beverages and this sometimes occurs," he said. "If you look at other religious and political people who have been wrongly incarcerated, you'll see others have gone through this."
Piccarreta, who represents Jeffs in two pending criminal cases, said he believed Mohave County handled the situation appropriately. Jeffs is more than 6 feet tall and has always been slight, Piccarreta noted.
"There's not a lot of extra pounds," he said.
Throughout his incarceration Jeffs has been known to fast and spend long periods on his knees in prayer.
Earlier this year, Mohave County's deputy jail director Bruce Brown told the AP that Jeffs had not had any significant health problems. Jeffs had been eating three meals a day and maintaining his weight, Brown said.
Jeffs is also facing criminal charges of bigamy and sexual assault of a child in Texas. The charges stem from information gathered by authorities during a raid on a church ranch near Eldorado last year.
The FLDS tie their religious roots to the early teachings of the mainstream Church of Jesus Christ of Latter-day Saints and practice polygamy in arranged marriages. The Mormon church renounced plural marriages in 1890 as part of Utah's push for statehood. Self-described Mormon fundamentalists such as the FLDS believe polygamy will bring glorification in heaven.
Jeffs, who is revered as a prophet who communicates with God, commands a flock roughly 12,000 strong despite his incarceration. Church members live mostly in the twin border towns of Hildale, Utah and Colorado City, Arizona. The faith also has small enclaves in Texas, Colorado, South Dakota and near Bountiful, British Columbia.