WASHINGTON (CNN) -- Blackwater USA guards have used deadly force weekly in Iraq and have inflicted "significant casualties and property damage," according to a congressional staff report released Monday that cites internal company and State Department documents.
Blackwater's contractors fired their weapons 195 times -- or an average of 1.4 times a week -- from the beginning of 2005 through the second week of September, the Democratic staff of the House Oversight and Government Reform Committee found.
In over 80 percent of the cases, Blackwater reports that its forces fired first, according to the staff report.
The committee will hear from Blackwater's CEO Erik Prince on Tuesday. Read Prince's prepared statement (PDF)
Records of the company and State Department show Blackwater's use of force in Iraq has been "frequent and extensive," the report says.
Though Blackwater is authorized to use force only defensively, "the vast majority of Blackwater weapons discharges are pre-emptive, with Blackwater forces firing first at a vehicle or suspicious individual prior to receiving any fire," the report states.
A Blackwater contractor wrote an initial U.S. government report describing contractors' involvement in a September 16 incident in which Iraqi civilians were shot, government and industry sources told CNN.
The Iraqi government claims Blackwater contractors, who were guarding a U.S. diplomatic convoy, killed as many as 20 civilians in western Baghdad's Nisoor Square.
The incident elicited outrage in Iraq and raised questions about the accountability of foreign security personnel in the country who, under an order by the U.S.-led occupation government, are not subject to Iraqi law.
Blackwater said its employees responded properly to an insurgent attack on a convoy, and the State Department "spot report" written by the Blackwater contractor underscores that and doesn't mention civilian casualties.
However, the contractor's account is at odds with Iraqis' version of the incident. A senior Iraqi National Police official participating in the Iraqi governmental probe of the shooting said the Blackwater gunfire was unprovoked and random, killing and wounding several civilians.
Blackwater contractor Darren Hanner drafted the two-page spot report on the letterhead of the Bureau of Diplomatic Security for the embassy's Tactical Operations Center, said a source involved in diplomatic security at the U.S. Embassy in Baghdad.
Hanner, listed on the report as the center's watch officer, was working for Blackwater at the time the report was written -- just after the shooting occurred, said a highly placed industry source. He was to rotate out of Iraq last week, the source said.
The center tracks and monitors all incidents and movements involving diplomatic security missions and has outsourced positions to Blackwater and another private firm, the embassy source said. Watch aftermath video of the shooting obtained by Newsweek »
The State Department is conducting an investigation, and deputy spokesman Tom Casey called the spot report "a first-blush account of those on the scene." He said the "report has no standing whatsoever."
"It was not intended to be used as an analysis, investigation, review or any detailed assessment of the situation. To assert that is untrue," Casey said.
A State Department agent took sworn statements from the participants in the shooting after receiving the spot report, the embassy source said.
A joint U.S.-Iraqi commission is expected to examine security and safety issues and will receive results of the State Department investigation and a separate Iraqi investigation, the U.S. military said.
The senior Iraqi police officer said Blackwater team members were questioned by Iraqi police immediately after the incident. The contractors first said they opened fire in response to a mortar attack, the officer said. However, the contractors then changed their story at least twice during the 90 minutes they were held, the officer said.
Iraqi police released a video of the aftermath of the shooting which shows a car that had damage consistent with a rocket-propelled grenade.
The video shows what appears to be the spent casing of a rifle-fired grenade, and the embassy source said the Blackwater guards were armed with a rifle-fired M-203 grenade.
The embassy source said a New York Times story reporting investigators were told that at least one guard drew a weapon on a fellow guard who did not stop shooting after colleagues called for a cease-fire was "pretty much true."
Blackwater previously denied reports that one Blackwater employee drew a gun on another. Learn more about private contractors working in Iraq »
The embassy source, meanwhile, said Blackwater is suffering a staffing shortage as it tries to meet its mission of guarding U.S. diplomats moving around Baghdad and other sections of Iraq.
Anne Tyrrell, a spokeswoman for Blackwater, denied that assertion.
"To my knowledge that's inaccurate," Tyrrell said. "I would urge caution in trusting the source."
As State Department investigators arrived in Baghdad from Washington to investigate the shooting, many of the guards involved had ended their contracts with Blackwater and were leaving Iraq, the embassy source said, speaking anonymously because he is not authorized to speak to the media.
The State Department official said as of Friday all guards that were involved in the incident were still in Iraq, except for one who had to be evacuated for medical reasons.
"It would be hard to do an investigation without the principal players there," the official said, referring to the State Department inquiries into the issue.
"We cannot take anybody out of the country during an investigation without U.S. government approval," Tyrrell said. "It is inaccurate that the 19 men being investigated have left Iraq."
Several of the guards involved in the shooting have requested disability severance and others have not renewed their expiring contracts, the State Department source said. None of those involved are being sent on security missions, he said.
The Iraqi government said it will file criminal charges against the Blackwater employees, according to Iraq's Interior Ministry.
It's not clear how Iraqi courts would attempt to bring the contractors to trial. E-mail to a friend
CNN's Jomana Karadsheh in Baghdad, Zain Verjee in Washington and Suzanne Simons in Atlanta contributed to this report.