The video has appeared on a Web site informally linked to London-based Aegis Defense Services Ltd., one of the biggest private security contractors in Iraq.
The words "Aegis PSD" appear in the clips, which seem to have been filmed out of the back of a vehicle traveling down a busy road, apparently carrying contractors. Sprays of gunfire, apparently from the vehicle, are seen hitting the road behind the vehicle, with cars swerving to avoid the fire. At one point, a car crashes after being hit by bullets.
The clip is set with a soundtrack of Elvis Presley's song "Mystery Train." No contractors appear in the video and the exact source of the gunfire can't be seen.
It is common for contractors and Iraqi troops and security forces to fire warning shots at vehicles that approach them too closely or too quickly on Iraq's roads, amid fears of suicide car bombings and other attacks that have killed hundreds of people.
Lt. Col. Barry Johnson, a military spokesman in Baghdad, said the military's Criminal Investigation Division has launched an inquiry into the video. He could not provide further details.
The existence of a U.S. military investigation was first reported by The Washington Post.
An Aegis spokeswoman, Sara Pearson, said a joint investigation with Aegis and the U.S. military began two weeks ago and its outcome could be released next week.
She said the probe aims to answer whether the video is connected to Aegis, whether Aegis employees did the shooting and whether it fell outside the rules of engagement.
Aegis released a statement last month after the video first arose saying its staff operated under strict rules of engagement that "allow for a structured escalation of force to include opening fire on civilian vehicles under certain circumstances." It said all such incidents were investigated.
Aegis was established in 2002 by Tim Spicer, a former British Army officer whose previous firm, Sandline International, was accused of providing mercenaries and arms to Sierra Leone in the 1990s in violation of a U.N. embargo.
It is unclear in the video whether any of the cars fired at were making threatening motions toward the vehicle from which it was filmed.
The U.S.-led coalition and private Western groups operating in Baghdad have come to rely on tens of thousands of private contractors for many security duties, including guarding facilities and some highways. Nearly 300 are reported to have been killed in Iraq. Some Iraqis have complained that the contractors have used excessive force.
By Elena Becatoros