Iranian officials had downplayed the fire, which could set back the country's development of advanced centrifuge models.
The Natanz nuclear site is one of the most-tightly guarded sites in all of Iran.
Tehran accuses Trump and 35 others of involvement in the January drone strike that killed Gen. Qassem Soleimani in Baghdad.
Fifteen other sailors were injured in the incident, Iran's navy said.
On Wednesday, Iran's Revolutionary Guard conducted a space launch and Trump threatened to "destroy" Iranian gunboats if they harass U.S. Navy ships.
The country has reportedly unveiled what experts described as a secret space program with a surprise launch.
U.S. policy stymies Iran's access to medicine and vital equipment, 32 members of Congress say in a letter shared exclusively with HuffPost.
Nearly 300 people have been killed and more than 1,000 sickened by ingesting methanol in the mistaken belief it protects against the new coronavirus.
A group of Democratic senators joined growing calls for Trump to ease punishing sanctions and provide aid to Venezuela and Iran amid the worsening pandemic.
President Trump said he "won't accept" that Levinson, who disappeared in 2007, has died. But administration officials said he may have passed "some time ago."