Reports from Iran Monday said a large explosion was heard in Isfahan, where several key nuclear facilities are located, including a uranium enrichment plant. Isfahan is one of the largest cities in Iran.

If accurate, the reported blast would be the second in nearly as many weeks, following an explosion that left 17 members of an elite Iranian army unit dead. That first explosion occurred at a military base outside the village of Bidganeh, about 40 kilometers (30 miles) southwest of Tehran and destroyed a missile base near the Iranian capital. An Iranian source later blamed Israel’s Mossad agency for the blast. 

Among those who were killed in the blast was Brigadier Hassan Moghadam, a researcher at a Tehran university who headed the Iranian Revolutionary Guards’ missile development program and the “Jihad Self-Reliance” unit.

The official Iranian FARS news agency initially reported on its website Monday that a loud blast was heard in the city at 2:40 p.m. local time. The report said that search and rescue teams were called to the scene but did not describe any injuries. A security official confirmed the explosion at the time, saying he had not received “exact information” but that the event was “under investigation.”

However, within the hour, the report was deleted from the news agency’s website. Subsequent inquiries by Iran’s Mehr news agency received a denial by the deputy governor of Isfahan province that there had been any explosion in the area.