The coalition said it was looking into the incident, but did not immediately comment.
The engineers and laborers had been building a road for the U.S. military in mountainous Nuristan province, and were sleeping in two tents in the remote area when they were killed Monday night, said Sayed Noorullah Jalili, director of the Kabul-based road construction company Amerifa. There were no survivors, he said.
"All of our poor workers have been killed," Jalili said. "I don't think the Americans were targeting our people. I'm sure it's the enemy of the Afghans who gave the Americans this wrong information."
The company has requested that the U.S. military investigate the source of its information, Jalili said.
Nuristan governor Tamim Nuristani said the coalition conducted airstrikes after receiving reports that "the enemy" was in the area, and hit the road construction workers as they were sleeping. Afghan officials often refer to the Taliban and other militants as "the enemy."
Jalili said the workers were from four nearby provinces, and that all but three of the bodies had been returned to their homes.
Earlier this year, foreign troops came under scathing criticism for conducting airstrikes based on poor intelligence and causing a number of civilian casualties.
Afghan President Hamid Karzai pleaded repeatedly with NATO and coalition troops to cooperate closely with their Afghan counterparts to prevent civilian deaths, and the number of such incidents dropped significantly in the past few months.
This has been the deadliest year yet since the U.S.-led invasion in 2001, and more than 6,000 people - a record number - have been killed in militant attacks and military operations, according to an AP tally of figures from Afghan and western officials.
Amerifa, an 11-year-old company, received the contract to build the road for the U.S. military last year, Jalili said.
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