CHERNOBYL - JANUARY 28: A Chernobyl sign on entry to the town is seen on January 28, 2006 in Chernobyl, Ukraine. Chernobyl and the surrounding area will not be safe for human habitation for several centuries. Scientists estimate that the most dangerous radioactive elements will take up to 900 years to decay sufficiently to render the area safe. (Photo by Daniel Berehulak/Getty Images)

CHERNOBYL, Ukraine (AP) — The head of the International Atomic Energy Agency says Russian troops risked causing an accident with their “very, very dangerous” seizure of the Chernobyl nuclear plant in Ukraine. Thirty-six years after the world’s worst nuclear disaster, agency Director-General Rafael Mariano Grossi said that while radiation levels at the damaged plant are normal, the situation is still “not stable.” he said Tuesday that nuclear authorities have to “keep on alert.” Russian troops moved into the radiation-contaminated Chernobyl exclusion zone in February on their way toward the Ukrainian capital. They withdrew late last month as Russia pulled its forces from areas near Kyiv and switched its focus to fighting in eastern Ukraine.