Updated

A U.S. Army Black Hawk helicopter went down south of Baghdad Wednesday, killing at least six soldiers and wounding four, Pentagon officials said.

Initial reports indicate that helicopter was downed by small-arms fire near Karbala, Pentagon officials said. The Euphrates River city was the site of fierce fighting between the Army's 3rd Infantry Division and Iraqi troops, including Republican Guard forces.

Later Wednesday, Brig. Gen. Vince Brooks, at the daily press briefing in Qatar, said the military was unsure what brought the Black Hawk down, Reuters reported.

"We had a Black Hawk helicopter that went down during operations yesterday," Brooks said.  "The investigation into that is ongoing. We do have some casualties as a result of that — we don't think as a result of hostile fire."

The Black Hawk was the second U.S. helicopter to go down in combat. An Army Apache assault helicopter went down March 24 during an assault on Republican Guard forces; its two pilots were captured by Iraqis.

There was some initial confusion about the downing Wednesday night. U.S. Central Command headquarters in Qatar issued an initial statement saying six were believed to have been aboard and "casualties have not been confirmed at this point."

But Pentagon officials said their initial reports showed seven soldiers aboard the helicopter were killed and four were wounded and rescued.

The UH-60 Black Hawk is one of the Army's main utility and troop transport helicopters. Each is flown by a crew of four and can carry up to 11 soldiers.

The helicopters are equipped with advanced avionics and electronics, such as global positioning systems and night-vision equipment.

A Black Hawk crashed in a remote, wooded area of Fort Drum, N.Y., during a training exercise last month, killing 11 of the 13 soldiers aboard.

In February, a Black Hawk crashed during night training in the Kuwaiti desert, killing all four crew members. The Kuwaiti military said sandstorms were reported in the area at the time the chopper went down.

In January, an MH-60, an adapted version of the Black Hawk, crashed during training near Bagram Air Base in Afghanistan, killing four members of an elite aviation regiment.