Four soldiers died when a modified Blackhawk helicopter on a training mission crashed Thursday near Kabul, military officials said today.

The Special Operations helicopter went down about 7:30 p.m. in an area eight miles east of the airbase that is used for aerial gunnery, and there was no indication of hostile fire, said Col. Roger King, a military spokesman. An investigation is underway. Training often is conducted at night because that is when many operations take place, King said.

It was the worst loss of life for U.S. forces in Afghanistan since March 4, 2002, when seven soldiers were killed and 11 wounded in an offensive against Taliban and al Qaeda forces.

King said the helicopter was an MH-60 Blackhawk modified for special operations. He did not identify the crew members, but said that all on board died.

King said that the rockets that are periodically fired at the airbase are almost always launched from the north, bolstering the view that the crash was not caused by hostile fire. The base is about 30 miles north of the capital, Kabul.

Since U.S. military action in Afghanistan began in October 2001, at least five U.S. helicopters have crashed or had hard landings that injured U.S. troops. Two Army Rangers and two Marines have been killed, and at least 11 other troops injured.

-- Marc Kaufman