The U.S. military says one of its helicopters crashed in southern Afghanistan, adding that the cause was unknown and there were no casualties.

In a statement, U.S. Army Col. Michael Lawhorn said Friday the helicopter made a "hard landing" in Helmand, but gave no details on timing or location.

He says all personnel have been recovered and an investigation is underway.

The Taliban claimed they shot down the chopper.

Helmand, a Taliban stronghold, has been the focus of intense military activity in recent months as the insurgents fight for control of lucrative drug smuggling routes.

The U.S.-NATO mission has 12,900 troops in Afghanistan mandated to train and assist their Afghan counterparts.

The U.S. also has 3,000 troops engaged in counter-terrorism operations against the Taliban, al-Qaida and the Islamic State group.