Haynes said that the workers, who are mainly from India, Nepal, Sri Lanka and Bangladesh, were living in three large warehouses.
"Inside them there are lines of bunk beds. Some of them have blankets, some of them say they don't," she said.
"They [the workers] said they had three meals a day but ... they only receive one and half litres of water a day and health care is minimum."
The labourers are contracted to Najlaa, a subcontractor to KBR, the Texas firm that split off last year from Halliburton.
A report by the McClatchy News Service on Tuesday also said that the workers had staged a march outside the warehouses to protest at their living conditions, which the news service said appeared to violate US military guidelines on minimum living spaces.
But Marwan Rezk, the general manager of Najlaa International Catering Services, denied that the labourers had been badly treated.
"They are living in a decent environment, provided three meals a day, showers and latrine facilities," he said.
The US military confirmed that it would look into the report.
Rezk told The Associated Press that the workers' contracts stipulate that they are to be paid when they begin working.
They are also compensated during the period they are waiting to go to work or when they are returned home rather than put to work, he said.
Rezk said the company has moved several hundred workers already to a work site and that they have been issued uniforms, meals, petty cash to call home and hygiene kits.
The other workers will be returned to their countries and will be compensated through their recruitment agents, he said.
The workers include labourers, clerks, chefs, nurses, medical technicians and doctors, Rezk said.