Iran's Defense Ministry says an "accident" in the Parchin area near Tehran occurred at one of its research units, killing one person and injuring another.
Parchin, some 60 kilometers southeast of Tehran, is a military base where the UN's nuclear watchdog, the International Atomic Energy Agency (IAEA), has previously said it suspected Iran conducted tests related to nuclear detonations more than a decade ago.
"On Wednesday evening, in an accident that took place in one of the research units of the Defense Ministry in the Parchin area, engineer Ehsan Ghad Beigi was martyred and one of his colleagues injured," the ministry said.
It did not elaborate on the cause of the accident or provide any further details, saying an investigation was under way.
Iran in 2015 allowed the IAEA to take environmental samples at Parchin to make an assessment of "possible military dimensions" of its nuclear program.
Iran says its nuclear program is solely for peaceful purposes, but it is now enriching uranium to up to 60 percent purity -- its highest level ever and a short technical step from weapons-grade levels of 90 percent.
In June 2020, an explosion caused by a tank leak occurred in the Parchin area at a gas storage facility.
Western concerns over the Iranian atomic program led to sanctions and eventually to Tehran's 2015 nuclear deal with world powers.
U.S. President Donald Trump in 2018 withdrew from the accord and reimposed harsh economic sanctions. Talks to revive the agreement resumed in Vienna last year but have lately stalled.
U.S. special envoy for Iran Robert Malley said on May 25 that the prospects of reviving the 2015 deal were "tenuous" at best, telling a Senate committee that it is more likely than not that talks will fail.