An engineer died and another employee was injured after an accident on Wednesday in a research center at the Parchin military site affiliated with Iran's Defense Ministry, the semi-official Fars news agency reported on Thursday.
Fars news said investigations into the cause of the accident were underway.
Situated 60km (37 miles) southeast of Tehran, Parchin is a sensitive military site housing several industrial and research units, where Western security services believe Iran carried out tests related to nuclear bomb detonations more than a decade ago.
In 2015, Tehran allowed the UN nuclear watchdog to take environmental samples at the military site to assess "possible military dimensions" of Iran's nuclear program.
Iran says its nuclear program is solely for peaceful purposes.
In June 2020, an explosion caused by a tank leak occurred in the same area at a gas storage facility.
On Wednesday, the Wall Street Journal (WSJ) reported that Iran has used classified documents from the UN's nuclear watchdog to cover up and conceal work on nuclear weapons
The New York-based daily cited Middle East intelligence officials and documents examined by it in its report.
According to the report, the documents — which were retrieved in an audacious clandestine operation of Israel's Mossad intelligence agency and exposed by then-prime minister Benjamin Netanyahu in 2018 — reveal how the Mullah regime in Tehran tried to hoodwink the International Atomic Energy Agency (IAEA) inspectors who sought to scrutinize its nuclear weapons program about two decades ago.