The coalition said it was looking into the incident in Nuristan province, but did not immediately comment. NATO's International Security Assistance Force said it has conducted airstrikes against Taliban fighters in the area, but did not say when.
"ISAF was engaged in Nurgaram and Du Ab (districts), and in those places we used airstrikes against (Taliban)," ISAF spokesman Brig. Gen. Carlos Branco told a news conference. "The situation is not clear at all at this stage. We are carrying out the investigation and trying to get a clear picture."
The engineers and laborers had been contracted by the U.S. military to build a road in mountainous Nuristan, and were sleeping in two tents in Nurgaram 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 report could not be independently verified because the area is difficult to reach.
The company has requested that the U.S. military investigate its information, Jalili said.
Nuristan Governor Tamim Nuristani said the coalition conducted air strikes 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.
NATO Secretary General Jaap de Hoop Scheffer said last week in Kabul that the alliance has "worked hard" to change its procedures to avoid civilian deaths, following U.N. criticism that the foreign troops were behind an alarming number of civilian casualties in Afghanistan.
Afghan President Hamid Karzai has 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, with more than 6,000 people 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 135 miles of road for the U.S. military last year, Jalili said.