The chief executive of Sofia-based Heli Air, Mihail Mihaylov, says his company will halt operations in Iraq. Mr. Mihaylov says he will arrive in Iraq Saturday to join in the investigation into the crash of the Russian-made helicopter and organize the return of the remains of the helicopters' three Bulgarian crewmembers. Two security guards from Fiji and six American employees of a civilian security company were also killed in the incident.

The U.S.-led coalition in Iraq has sent an investigative team to the site of the crash, but officials say it is still too early to confirm its cause.

A group calling itself the Islamic Army in Iraq has posted a video tape on the Internet showing Islamic militants capturing and shooting the lone survivor of the incident. Another group, the Mujahedeen Army, has also taken responsibility for shooting down the helicopter.

Mr. Mihaylov told VOA that it was difficult for him to watch the videotape of the incident because he knew Lyobomir Kostov, the 42-year-old Bulgarian captain of the helicopter who was killed after the crash. "This is a tragedy. He was alive and they killed him. He was a captain of the helicopter. He was around the helicopter, alive, but with a broken leg. They [the militants] helped him, but then killed him," he said.

The crash comes at a time when Bulgaria, one of several Eastern European countries involved in U.S.-led operations in Iraq, is considering withdrawing its 460 troops from the country by the end of the year.

Bulgaria's government has come under increasing public pressure, after eight soldiers were killed earlier in several attacks, including what was called "a friendly fire incident" in March.