WASHINGTON — Members of a polygamist sect have built a network of construction companies in Western states that recently have won millions of dollars in public works contracts by making extremely low bids.

Critics of the Fundamentalist Church of Jesus Christ of Latter Day Saints say the successes of these companies stem from cheap labor that include young men performing church mission work at little or no pay as part of their religious obligation to the sect.

The sect drew national attention this month after the Texas Department of Family and Protective Services removed 416 children from the sprawling 1,700-acre Yearning for Zion Ranch near Eldorado, Texas, amid allegations of child sexual abuse. The children were removed and their mothers left voluntarily from the vast 79-building complex that carries an appraised value of $21 million.

Among the most successful enterprises run by members of the sect are at least three construction and contracting companies based in Hildale, Utah. The largest of these is JNJ Engineering Construction Inc. owned by sect member Jacob Nathan Jessop for whom the company is named.

"If you don't have to pay for labor, you can really underbid for contracts. It has become a huge problem for other contractors," said Flora Jessop of Phoenix, the contractor's cousin.

Government procurement officers say they have been surprised at the dramatically low bids JNJ has submitted in recent years.

"We were nervous because their bid was so much lower than anyone else's," said Pamela Lynn, senior procurement officer of the Mohave County, Ariz., procurement department.

JNJ Engineering successfully bid $419,994 in January to win a contract to make improvements to the Lake Juniper Water System in Arizona, beating the second lowest bidder by more than $125,000. Since the firm was the lawful low bidder, Mohave County accepted the bid even through officials were very much aware of Jessop's ties to the polygamist group.

"They didn't have any criminal record or anything like that," Lynn said. "We never take anyone's religious affiliation into account, of course."

The firm won 13 contracts totaling more than $11 million with the Las Vegas Valley Water District from 2004 through 2007, all awarded to the lowest bidder.

"They do submit bids that are quite a bit lower than our engineer's estimate," said water district spokesman Bronson Mack. "But they don't get every contract that they bid, not in the least."

He said the firm has a good reputation.