Military officials say the OH-58 Kiowa helicopter, which was armed, responded to assist Iraqi police who were under small arms fire from the ground, reports CBS News' Pete Gow in Baghdad.
Lt. Col. Barry Johnson, a U.S. military spokesman in Baghdad, said the causes of the crash were under investigation.
Meanwhile, hundreds of Iraqi police candidates left restive Anbar province Friday for training in the capital, including 200 men who survived a suicide bomb attack last week that killed 58 people.
In other developments:
In Ramadi, half of the 400 police candidates that left for Baghdad were from Qaim, a frontier Anbar town near the Syrian border that has been the scene of repeated fighting between U.S. forces and insurgents — including many foreign fighters infiltrating from neighboring Syria. Anbar is predominantly Sunni Arab and is the focal point of much of the insurgency in Iraq.
The other 200 candidates were from Ramadi, an insurgent hotbed where hundreds of police recruits were targeted near the Ramadi Glass and Ceramics Works.
"On Jan. 5 a suicide bomber attacked the recruitment center in Ramadi killing more than 30 applicants. Despite that attack, the recruits returned en masse today," Marine Capt. Jeffrey S. Pool said.
The men are part of an effort to return police to Anbar, including Ramadi and nearby Fallujah.
"There are approximately 1,200 Iraqi police officers patrolling the streets of Fallujah with 400 more attending the Baghdad Police Academy. This is the first large group of Iraqi Police candidates from Ramadi and the Western Euphrates River Valley to attend the Ministry of Interiors police training," Pool said in announcement from Ramadi.
U.S. soldiers from 2nd Brigade Combat Team assisted in providing security for the convoy to Baghdad, he addded.
U.S.-led coalition forces are helping train police and army units as part of effort to turn over security and the fight against the insurgency to Iraqi security forces.
The U.S. military has predicted that more violence will engulf Iraq in the weeks ahead as the country's splintered politicians and religious groups struggle to form a government.
Thursday's warning followed a week marked by what U.S. Brig. Gen. Donald Alston described as "horrific attacks," amid deteriorating relations between the Iraq's largest Shiite religious group and Sunni Arabs who make up the core of the opposition.
Alston, spokesman for the U.S.-led coalition force, said attacks that have killed at least 500 people since the Dec. 15 elections were a sign insurgents were using the difficult transition to a new government to destabilize the democratic process. In the month since the elections, 54 U.S. forces also have been killed.
Violence dropped after Iraqis began celebrating the four-day Islamic feast of sacrifice, Eid al-Adha, on Tuesday. But Alston said it was likely to rise.
"As democracy advances in the form of election results and government formation, and as the military pressure continues, and the pressure generated by political progress increases, we expect more violence across Iraq," Alston said at a news briefing.
Final election results have been delayed by Sunni Arab complaints of fraud, but are expected next week. Although leading politicians have expressed hopes a government could be formed in February, most experts and officials agree it could take two to three months, as it did after the Jan. 30 elections for an interim government.
The governing United Iraqi Alliance, a Shiite religious bloc, has a strong lead, according to preliminary results. But it won't win enough seats in the 275-member parliament to avoid forming a coalition with Sunni Arab and Kurdish parties.
Alston said that as a new government starts forming, "those committed to seeing democracy fail will see this time of transition as an opportunity to attack the innocent people of Iraq."
He said the recent attacks, blamed mostly on extremists like Abu Musab al-Zarqawi's al Qaeda in Iraq, were part of an "attempt to discredit and derail the progress of the Iraqi people."
At least 121 people were killed last week in twin suicide attacks against a Shiite shrine in the holy city of Karbala and the Ramadi recruiting center. A day earlier, 32 people were killed by a suicide bomber at a Shiite funeral in Muqdadiyah. Twenty-nine more died in an attack Monday on the Interior Ministry compound in Baghdad.
"The increase in attacks across Iraq this past week clearly indicates that al Qaeda and others terrorists still have the capability to surge," Alston said.
Sunni Arab politicians, meanwhile, expressed anger over remarks by Iraq's most powerful Shiite politician suggesting that the new constitution, approved in October, would not be amended.
A key Sunni demand is weaker federalism and a stronger central government. The constitution now gives most power — including control over oil profits — to provincial governments. The Shiites in the south and the Kurds in the north control nearly all of Iraq's oil.