As emerging evidence has begun to cast doubt on initial explanations for the deaths last week of two Reuters staff members, the news service has asked the Pentagon to conduct an investigation into the killings.

Photographer Namir Noor-Eldeen, 22, and driver Saeed Chmagh, 40, were killed in Baghdad Thursday in what witnesses have said was a U.S. helicopter attack that a preliminary police report described as “random American bombardment.” The U.S. military said in a statement that the incident was a firefight with insurgents, and the killings are being investigated.

“Our preliminary investigation raises real questions about whether there was fighting at the time the two men were killed,” David Schlesinger, editor-in-chief of Reuters was quoted as saying in a Reuters article. “For the sake of their memory and for the sake of all journalists in Iraq, we need a thorough and objective investigation that will help us and the military learn lessons that will improve the safety of journalists in the future.”

Residents and witnesses interviewed by Reuters said they saw no gunmen in the area the two men were killed, and they were not aware of any clashes in the al-Amin al-Thaniyah neighborhood leading up to the Apache helicopter attack at 10:30 am local time Thursday.

The U.S. military returned to Reuters two digital cameras that belonged to Noor-Eldeen on Thursday. Neither camera contains photos showing clashes between U.S. forces and militants.

Schlesinger said Reuters wants the following from the U.S. military in Baghdad: Why the cameras were confiscated, access to any cameras onboard the Apache helicopters involved in the incident, access to any voice communications between the helicopter crews and ground forces and access to reports from the unit involved in the incident.