A helicopter carrying security forces crashed in western Afghanistan, killing all five people on board, including the pilot, officials said on Saturday, but ruled out a militant attack.

A wave of assaults by Taliban militants in recent weeks has forced Afghan and foreign forces to make far greater use of air transport to move troops and supplies, but inadequate training and poor planning have led to frequent crashes.

The latest crash was caused by technical difficulties rather than a militant attack, said Naser Mehri, a spokesman for the governor of Farah province, site of the accident.

“The helicopter crashed due to a technical issue, not due to Taliban fire,” Mehri said.

The cause of the crash is being investigated, said a defense ministry official in Kabul, the capital, adding that the helicopter had been transporting Afghan security forces.

The Taliban are fighting to expel foreign forces, defeat the government and impose their version of Islamist rule after their 2001 ouster by U.S.-led troops.