A fire was reported at the Zaporizhzhia nuclear power plant in southeastern Ukraine early on Friday, according to Ukrainian officials. (Zaporizhzhia NPP)Ukrainian authorities said a fire that broke out at a nuclear power plant early Friday amid heavy shelling by Russian forces has now been extinguished.Here’s what happened:When did the fire start? Ukrainian authorities said about 2:30 a.m. local time Friday that a fire had broken out at the Zaporizhzhia nuclear power plant, located in Enerhodar, southeastern Ukraine. The plant is the largest of its kind in Ukraine and contains six of the country’s 15 nuclear energy reactors, according to the International Atomic Energy Agency (IAEA).When did the blaze stop? The Ukrainian State Emergency Service said the fire at the plant’s training building was extinguished at 6.20 a.m. No deaths or injuries were reported, according to the statement.Are they still fighting? Fighting has since stopped in the area, a spokesperson for the power plant told CNN. In a Facebook post early Friday, Ukrainian President Volodymyr Zelensky accused Russia of intentionally firing at the nuclear plant — and urged European leaders to “wake up now” and stop Russian forces “before this becomes a nuclear disaster.” How serious is the situation? It’s hard to say since there is still a lot we don’t know. But the plant has not sustained any “critical” damage, the spokesperson for the facility said. The fire has not affected any “essential” equipment, and staff are taking action to mitigate any damage, the IAEA said, citing Ukrainian authorities.Are we seeing any radiation spikes? No — nuclear regulators and government bodies in the United States and Ukraine say radiation levels appear normal.What are the risks? The worst-case scenario would be if a fire or attack reached the reactors, disrupted their cooling system and caused a meltdown, which would release large amounts of radioactivity. However, Graham Allison, professor at the Belfer Center, Harvard University, told CNN early Friday that “not all fires in a power plant, have catastrophic consequences.”