ENERHODAR, Ukraine — External electricity was restored to the Zaporizhzhia Nuclear Power Plant on Sunday, hours after Europe’s largest nuclear station had to switch to diesel generators, the International Atomic Energy Agency said.

The Russian-controlled site has stopped generating electricity, but it still needs power for cooling nuclear fuel. The latest disruption began when the Ferosplavna line disconnected. The agency said the cause and location of the disconnection were unknown.

Russian-installed managers said the line’s protective system shut it down and that radiation readings at the plant and in the surrounding monitoring area remained normal. Ukraine’s nuclear operator also confirmed the temporary switch to generators.

The agency counted 27 losses of off-site power at the site since the war began. A local ceasefire in September allowed repairs after an earlier outage. The agency reported in October that the plant’s principal Dniprovska line was still unavailable.