A letter from a doctor says polygamous sect leader Warren Jeffs is being force-fed in an Arizona jail to prevent the possibility of "imminent death."

In a letter filed with the Mohave County Superior Court on Monday, county jail Medical Director Kirsten Mortenson told a judge that Jeffs has been refusing to eat and is no longer urinating. She says Jeffs's vital signs are worsening and he is suffering from malnutrition.

Mortenson says the jail, which is in Kingman, began force-feeding Jeffs on Friday and will continue monitoring him until his condition improves.

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.