Iranian authorities say an explosion reported at a military plant late Saturday was caused by an “unsuccessful” drone attack. Footage released in local media showed the blast at a purported ammunition factory in the central city of Isfahan. The Iranian Defense Ministry, in a statement released through state media, said, “an unsuccessful attack was carried out using (drones) on one of the workshop complexes of the Defense Ministry. …One of (the drones) was hit by the ... air defense and the other two were caught in defense traps and blew up.” The ministry did not name any groups suspected of involvement. News of the explosion came as a huge fire broke out at an oil refinery in the northwestern part of the country, with the cause not immediately clear. A 5.9-magnitude earthquake also struck the same area late Saturday, killing at least three people.