Kabul, Afghanistan (CNN) -- Three Drug Enforcement Administration personnel were among 14 Americans killed when three helicopters went down in Afghanistan on Monday, a law enforcement source said.
They were the first DEA personnel to be killed in Afghanistan. NATO's International Security Assistance Force said that in all, 10 people died in one incident and four in the other.
It was the largest number of Americans killed in Afghanistan in a single day in more than four years, according to CNN records. ISAF ruled out enemy fire in the crash that killed four Americans and said that enemy action was not thought to be the cause of the other.
