According to Associated Press reports, the nuclear power plant in the southern Ukrainian city of Enerhodar was shelled by Russian troops, and the facility caught fire. Plant spokesman Andriy Tuz told the AP that shells were falling directly on the plant and that one reactor — which had been under renovation and not operating, but still contains nuclear fuel — was on fire. He added that firefighters could get to the scene because of the fighting. The plant reportedly has six reactors, and three had been offline before the attack.

Shorty before midnight Eastern, Ukrainian officials said the fire had been extinguished.

Stock futures recovered as reports indicated no imminent disaster. There was some confusion about the details; a Reuters correspondent reported that the fire broke out at a training building outside the plant’s perimeter, and a Ukrainian regulator told the International Atomic Energy Agency there were no signs of increased radiation at the site and that the fire “has not affected ‘essential’ equipment.”

In a series of tweets, U.S. Energy Secretary Jennifer Graholm called Russia’s military operations at the plant “reckless,” but said “We have seen no elevated radiation readings near the facility” and added that the reactors are being safely shut down.

As the fire burned, Dmytro Kuleba, Ukraine’s minister of foreign affairs, tweeted that potential fallout could be worse than Chernobyl, and said “Russians must IMMEDIATELY cease the fire, allow firefighters, establish a security zone!”

According to experts, the risk lies if the plant loses power and is unable to cool the nuclear material — leading to a meltdown, which could be accompanied by an explosion.

Crude prices continued their surge, with April West Texas Intermediate crude futures
CLJ22,
+1.26%
near $110 a barrel and May Brent crude
BRNK22,
+0.91%,
the global benchmark, above $112 a barrel.

Stock futures had been little changed before news of the attack.

During the regular trading day, the stock market failed to hold onto gains. The Dow Jones Industrial Average
DJIA,
-0.29%
closed down 96.69 points, or 0.3%, to 33,794.66; the S&P 500
SPX,
-0.53%
 fell 23.05 points, or 0.5%, ending at 4,363.49; and the Nasdaq Composite
COMP,
-1.56%
 ended 214.07 points lower, or 1.6%, finishing at 13,537.94.