A huge blast at a military base in Iraq early on Saturday killed a member of an Iraqi security force.
The force commander said it was an attack while the army said it was investigating and there were no warplanes in the sky at the time.
Two security sources had said earlier that an airstrike caused the blast, which killed a member of Iraq's Popular Mobilization Forces (PMF) and wounded eight others at Kalso military base about 50 km (30 miles) south of Baghdad.
In a statement, the PMF said its chief of staff Abdul Aziz al-Mohammedawi had visited the location and "reviewed the details of the investigative committees present in the place that was attacked".
The Iraqi military said a technical committee was looking into the cause of an explosion and fire at the base, which it said happened at 1:00 am on Saturday (2200 GMT Friday).
"The air defence command report confirmed, through technical efforts and radar detection, that there was no drone or fighter jet in the air space of Babil before and during the explosion," the military said in a statement.
The incident in Iraq's Babil province occurred with tensions running even higher than usual across the Middle East, following what sources said was an Israeli attack in the Iranian city of Isfahan on Friday. Tehran has played it down and indicated it had no plans for retaliation.
That incident came six days after Iran fired a barrage of missiles and drones at Israel in response to a presumed Israeli airstrike that destroyed part of Iran's embassy in Damascus, killing seven Iranian Revolutionary Guards officers on April 1.