While an initial report blamed the fire on a militant attack, a subsequent statement from the U.S. Army denied there was an attack, saying it was simply an accident, KUNA reported.

The Army's report was confirmed by Maj. Gen. Raed Jawad, head of operations in Karbala.

"The fire was an accident caused by maintenance workers," Jawad said.

Both Jawad and the U.S. Army confirmed the Friday's fire had been controlled by firefighters.

A unidentified medical source told the Kuwaiti news agency four of the Iraqis injured in the pipeline fire were in critical condition.