Many, if not all, were special operations forces, the official said. If the numbers are confirmed, the incident would be the most deadly for coalition forces in the Afghan war, according to a CNN count of international troop deaths.
Afghan President Hamid Karzai issued a statement saying as many as 31 U.S. special forces and seven Afghans were killed and offered "deep regret" to U.S. President Barack Obama.
The Taliban claimed militants downed the helicopter with a rocket-propelled grenade. Mohammad Hazrat Janan, head of the provincial council said Tangi village elders reported that insurgents shot at the craft when it was flying back from an operation.
The incident took place in the eastern province of Wardak, an area rife with insurgent activity. There has been a swell of recent attacks in the country's southern and eastern provinces.
