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Radiation levels in the Chernobyl exclusion zone spiked 17 times over the normal background reading Sunday, the head of Ukraine's ecological watchdog said Sunday, as forest fires blazed about 12 miles into the Chernobyl disaster area.

"There is bad news," ecological inspection chief Yegor Firsov wrote in a Facebook post from the closed Chernobyl region. "At the center of the fire, radiation levels are high ... readings are 2.3, when the normal level is 0.14."

Firsov's post included a video of a Geiger counter, a device used to measure radiation levels.

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A Geiger counter measures a radiation level at a site of fire burning in the exclusion zone around the Chernobyl nuclear power plant outside the village of Rahivka, Ukraine, on Sunday, April 5, 2020. Yaroslav Yemelianenko / Reuters

According to Firsov, the alarming jump in radioactivity was found only in the center of the fire. In a later post Sunday, he wrote that nuclear specialists had charted no increase in radiation levels in the capital, Kyiv, only about 60 miles from the Chernobyl exclusion zone.

Ukrainian authorities said the fire, which engulfed an area of more than 250 acres over the weekend, was most likely caused by human negligence. Firsov said the blaze was likely the result of someone's setting fire to grass, which then spread to trees.

The Ukrainian Emergency Services Ministry said the fire had been extinguished. Radiation levels in the zone are within normal limits, the statement said.

Ukraine sees spikes in human-sparked forest fires annually, typically in the spring and the fall, according to the Emergency Services Ministry. Such fires are more dangerous around Chernobyl, as the trees and plant life are still irradiated from the 1986 nuclear disaster.

Firsov used the radiation spike to call for increasing fines for sparking forest fires. Currently, the fine is about $6.50 for committing arson. "This can't continue. The fine must go up 50-100 times," he wrote on Facebook.

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The head of Ukraine's emergency services, Andrii Vatolin, was less diplomatic. As firefighters returned home from the exclusion zone after two days of battling radioactive blazes, he was quoted on the ministry's Facebook page as saying those responsible for the fire were criminals.

"My indignation is in the fact that the firefighters who are forced to work in the exclusion zone are not liquidating the consequences of an accident, but the consequences of human negligence and criminal acts."