Suicide bombers killed seven people and wounded 12 in an attack on a power plant north of Baghdad on Saturday, an Iraqi security official told Agence France Presse.

Armed with grenades and wearing explosives belts, three attackers entered the facility in Samarra, about 100 kilometers north of the capital, at 2:00 am, the official said.

“They attacked the plant’s workers, killing seven and wounding 12, according to an initial assessment,” said the official.

Security reinforcements then arrived on the scene, killing two of the bombers and evacuating the employees.

There was no immediate claim of responsibility for the attack, but ISIS frequently carries out suicide bombings in Iraq.