HOUSTON—The U.S. Department of Labor, hit with complaints about possible workplace violations during Hurricane Ike recovery efforts, is investigating whether roofing subcontractors have been mistreating laborers.

At issue is the “blue roof” program overseen by the U.S. Army Corps of Engineers. More than 26,000 such temporary tarp roofs have been installed in 24 counties affected by the storm, costing U.S. taxpayers more than $21 million so far.

Laborers working for various blue roof subcontractors have been complaining of broken promises of lucrative pay—and possible violations of federal labor rules, officials say.

John Robinette of Dallas said he responded to an Internet ad about a huge payday for workers who install the blue tarp roofs under the federal recovery program. But when he got to the Houston area, he found a crowded Pasadena laborer camp that had no water or electricity. The big payoff never came and he quit within a week. He said he just recently got two checks for a total of $160.

Robinette lost $600 on gas and lodging, meanwhile.

Under federal rules, laborers are supposed to get weekly pay, plus any overtime, for wages based on the job performed.

The blue roof program is designed to provide temporary repairs for people whose roofs were damaged by the hurricane. Mike DeMasi, deputy director for project management in Corps’ Galveston office, said federal officials have heard complaints that worker rules were violated and that contractors were not withholding taxes as required.