News of the incident near the restive town of Falluja, west of Baghdad, came as US authorities released about 60 Iraqis from what was Saddam Hussein's most notorious prison, the first batch to be set free under a new amnesty program.

At the Abu Ghraib prison near the capital, which once housed Saddam's enemies, the freed inmates were brought out in two open trucks late in the afternoon and let out a mile away.

Honking their car horns and raising huge clouds of dust, hundreds of people who had been waiting outside the jail all day set off in pursuit. Later, they surrounded the freed men, searching desperately for friends and relatives.

Many of those released looked relieved but some were bitter.

"I'm very happy to be free," shouted Kamal Risaeya, 32, an identification tag still hanging from his leg. "I'm just looking forward to seeing my family."

Risaeya said he was detained in Saddam's hometown of Tikrit and held for five months. He said he was not harmed in custody.

But another man, who refused to give his name, said he had been mistreated. His voice shaking with anger, he said: "I'm free, but now I will attack them."

The downed Black Hawk was on a medical evacuation mission with four crew and four passengers aboard, the military said.

"There are no survivors," a US military spokeswoman said.

Another spokesman said all were US soldiers but neither knew if it had come under fire.

Last week, an OH-58 observation helicopter was shot down by guerrillas near Falluja. One pilot died, the other was wounded.

Thursday's crash was the deadliest helicopter incident for Americans in Iraq since Nov. 15, when two Black Hawks collided under fire near the town of Mosul, killing 17 soldiers.

AMNESTY FOR DETAINEES

Paul Bremer, the US administrator in Iraq, announced the amnesty Wednesday, saying low-threat detainees rounded up since April and held without charges would be released as part of efforts to promote reconciliation with Iraqis.

US forces have seized around 9,000 suspects over the past eight months, most of whom are being held at Abu Ghraib.