Iran’s defense ministry says the loud explosion heard at a military plant in Isfahan, and apparently a flash of light, was the result of an “unsuccessful” drone attack, state media reported Sunday.

“One of (the drones) was hit by the air defense, and the other two were caught in defense traps and blew up. Fortunately, this unsuccessful attack did not cause any loss of life and caused minor damage to the workshop’s roof,” state news agency IRNA reported.

Who fired the drone is unclear, but the incident and announcement this weekend come amid tensions with Israel over Iran’s nuclear program.