KYIV, Ukraine (AP) — Ukraine’s nuclear energy regulatory agency says that higher than usual gamma radiation levels have been detected in the area near the decommissioned Chernobyl nuclear plant, after it was seized by the Russian military.

The State Nuclear Regulatory Inspectorate said Friday that higher gamma radiation levels have been detected in the Chernobyl zone, but didn’t provide details of the increase.

It attributed the rise to a “disturbance of the topsoil due to the movement of a large amount of heavy military equipment through the exclusion zone and the release of contaminated radioactive dust into the air.”

Ukrainian authorities said that Russia took the plant and its surrounding exclusion zone after a fierce battle Thursday.

A Soviet-era top secret over-the-horizon radar system once used as part of the Soviet missile defense early-warning radar network, seen behind a radioactivity sign in Chernobyl, Ukraine, on Nov. 22, 2018. Among the most worrying developments on an already shocking day, as Russia invaded Ukraine on Thursday, was warfare at the Chernobyl nuclear plant, where radioactivity is still leaking from history’s worst nuclear disaster 36 years ago. (AP Photo/Efrem Lukatsky, File)

Russian Defense Ministry spokesman Maj. Gen. Igor Konashenkov said Russian airborne troops were protecting the plant to prevent any possible “provocations.” He insisted that radiation levels in the area have remained normal.

The Vienna-based International Atomic Energy Agency said it was told by Ukraine of the takeover, adding that there had been “no casualties or destruction at the industrial site.”

The 1986 disaster occurred when a nuclear reactor at the plant 130 kilometers (80 miles) north of Kyiv exploded, sending a radioactive cloud across Europe. The damaged reactor was later covered by a protective shell to prevent leaks.