Russian authorities claimed Tuesday to have put out a large wildfire that raged for several days over an area of radioactive contamination in Russia's central Ural region.

A wildfire burned "during the (May 9th) holidays in the zone of nuclear contamination," said the governor of Chelyabinsk region, where Mayak, Russia's facility that treats nuclear waste, is located.

"It was successfully stopped," governor Mikhail Yurevich said, Interfax reported.

The announcement came after Russian Greenpeace said on its forum Tuesday that the fire over the contaminated area has grown over two days, calling it "one of the most threatening current events connected with forest fires."

The site was contaminated during the so-called Kyshtym disaster in 1957 following an explosion at Mayak that broke a container holding radioactive waste, which prompted evacuation of nearly 13,000t people from the area.

It is measured as a Level 6 disaster on the scale of the International Atomic Energy Agency.

Russia's emergency situations ministry said in a note on Tuesday morning that a "large fire" on Mayak's contaminated territory in Chelyabinsk region continues to burn over 200 hectares.

In recent years, only areas with the highest fallout are restricted from agricultural and other use, according to the ministry's regional website monitoring radiation.

"It can't really be called radioactive trace by now," said governor Yurevich, claiming that contamination "went 40 centimeters deep into the ground" and is "no longer a problem."

Russia last summer found itself unprepared for a major calamity when an unprecedented heatwave coupled with noxious smog from burning peat bogs around Moscow wiped out the harvest and doubled mortality rates in the capital.

President Dmitry Medvedev lashed out at officials last month for failing to carry out preventive measures to avoid a repeat of wildfire crisis, warning that he will send them to fight fires in person if needed.

However environmental NGOs have said that officials are concealing information about fires or announcing threatening fires after claiming that they have already been extinguished.