WASHINGTON (CNN) -- The Army is investigating the possibility three soldiers of the 101st Airborne Division who died in a firefight in Iraq may have been killed by friendly fire, according to U.S. military officials.

Those officials emphasized it is not yet certain how the soldiers were killed January 8, but confirmed their families were notified of the friendly fire possibility.

The incident took place southwest of Samarra, when the unit, on patrol, discovered buildings filled with explosives and weapon-making material. After further searching, they encountered more than a dozen insurgents fighting from a network of tunnels and trenches.

In the ensuing firefight, helicopters and other aircraft were called to attack targets. The officials said it's possible three of the troops died as a result of those airstrikes.

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Pfc. Ivan Merlo, 19, of San Marcos, California, and Pfc. Phillip Pannier, 22, of Washburn, Illinois, died at the scene. Sgt. David Hart, 22, of Lake View Terrace, California, died later, the military said. E-mail to a friend

All About Iraq War • U.S. Army