Officials at the American Embassy and in the United States-led coalition force said they could not comment on specific cases.

Several e-mail messages and telephone calls to Sarah Lee, the president of Bennett-Fouch, the company offices and other employees were not answered, and Ms. Lee did not return three messages left on the voice mail of her number in the United States.

Lt. Col. Michael T. Lawhorn, a senior military public affairs officer in Afghanistan, said previous reports of Afghan companies not being paid for contracted work had turned out to be problems of incomplete or improperly filed paperwork.

Officials with the Afghan companies said they believed that they had been cheated. Two foreigners working in southern Afghanistan who were familiar with Bennett-Fouch said its managers had left Afghanistan owing Afghan companies up to $5 million.

One who spoke on the condition of anonymity said the company was using money owed to subcontractors to set up a sister company, K5 Global; the military official said Bennett-Fouch ran into trouble after a concrete and asphalt batching plant it bought in Afghanistan failed because of poor construction.

“The subcontractors out here are very unlikely to be able to hire an attorney in the U.S., and thus the chances of seeing any payment is really zero,” the ISAF military official said.

As the United States military contingent in Afghanistan rises to nearly 100,000 troops, millions of dollars are being spent to expand the military bases and build extra forward operating bases, as well as training centers, bases and outposts for the expanding Afghan Army and police forces. The bulk of the construction work is handled by American companies who frequently subcontract to one or more layers of smaller companies.