Most of the more than 100 private security companies in Iraq open fire far more frequently than has been publicly acknowledged and rarely report such incidents to U.S. or Iraqi authorities, according to U.S. officials and current and former private security company employees.

Violence caused by private security guards in Iraq has come under scrutiny since a Sept. 16 shooting in Baghdad involving employees of Blackwater USA. The company’s chairman, Erik Prince, told a congressional committee Tuesday that Blackwater guards opened fire on 195 occasions during more than 16,000 missions in Iraq since 2005.

However, two former Blackwater security guards said they believed employees fired more often than the company has disclosed. One, a former Blackwater supervisor who spent nearly three years in Iraq, said his 20-man team averaged “four or five” shootings per week, or several times the rate of 1.4 incidents per week reported by the company. The underreporting of shooting incidents was routine in Iraq, according to this former guard.

“The thing is, even the good companies, how many bad incidents occurred where guys involved didn’t say anything because they didn’t want to be questioned or have any downtime today to have to go over what happened yesterday?” he said. “I’m sure there were some companies that just didn’t report anything.”

The former Blackwater guards and other private security guards spoke on condition of anonymity because of concerns they would be unable to obtain future employment in the security industry. In addition, Blackwater employees reportedly sign an agreement pledging not to divulge confidential information; violations can result in a $250,000 fine imposed by the company.

Tens of thousands of private security guards operate in Iraq under a multitude of contracts, each with its own regulations. Defense and State Department contracts require security companies to report all weapons discharges, but few comply fully, according to U.S. officials and security company employees. Two company officials familiar with the system estimated as few as 15 percent of all shooting incidents are reported, although both cautioned it was impossible to know exactly how many incidents go unreported.

Out of nearly 30 security companies under Defense Department authority, only “a handful” have reported weapons discharges, said Maj. Kent Lightner of the U.S. Army Corps of Engineers, who monitors shooting incidents involving security companies under military contracts. Lightner said the lack of reporting undermines statistics the military compiles on shooting incidents. Through May, the military had reported 207 such incidents over the previous 12 months.

Col. Timothy Clapp, who preceded Lightner as director of the Reconstruction Operations Center, which tracks the movements of private security firms under Defense Department contracts, said reported incidents were usually limited to a few companies, including two British firms, Aegis Defence Services and ArmorGroup International.

Clapp said military officials became temporarily concerned last year that Aegis, which protects Corps of Engineers officials on reconstruction projects, was “out of control” because the company reported so many incidents. But Clapp said the numbers were skewed because Aegis conducts many more missions than other companies and because other companies rarely or never report shooting incidents.

“In their contracts, it says they are supposed to report, but whether they do or not is up to them,” he said.

U.S. officials and security company representatives said they were especially concerned about firms that operate beyond the radar of U.S. and Iraqi authorities. David Horner, who worked for Crescent Security Group, a company based in Kuwait City, said that after being attacked with a roadside bomb in a town north of Baghdad, Crescent employees fired their automatic weapons preemptively whenever they passed through the town.

“I know that I personally never saw anyone shoot at us, but we blazed through that town all the time,” said Horner, 55, a truck driver from Visalia, Calif. “Personally I did not take aim at one person. But I don’t know what everybody else did. We’d come back at the end of the day, and a lot of times we were out of ammo.”

Horner said he did not believe any of the incidents were reported to the military. He said he quit after one of Crescent’s Iraqi employees fired a belt-fed PK machine gun from the bed of Horner’s truck and hit what appeared to be two members of the Iraqi National Guard.

“I was like, ‘Oh man, we shot some of our own guys,’ ” Horner said. He said he consulted with the Crescent team leader as the two Iraqis writhed in pain, one shot in the legs, the other with “a bullet or two in his shoulder.” Soldiers from a nearby Iraqi army checkpoint were approaching to investigate.

“That was my last mission,” Horner said. “I wasn’t over there to wreck somebody’s life. There was too much cowboying going on. I really didn’t know if we had made things worse over there. More than likely we did; that was my feeling.”

Lightner, the Army major who monitors shooting incidents, said he thought the number of reported incidents was in some ways insignificant. “If Aegis sends me a report and says, ‘Bad guys shot at us; we shot back and dropped two of them,’ I’m not going to investigate. I’m not going to worry about it unless somebody comes back and says, ‘Yeah, they dropped two children, or they dropped a woman.’ ”