MOSCOW — A major fuel spill in Siberia has prompted Russian President Vladimir Putin to declare a state of emergency in an environmentally sensitive Arctic region after publicly scolding local authorities for what he said was a botched response.

A fuel tank at a power plant ruptured Friday in Norilsk — above the Arctic Circle in north-central Russia — leaking at least 20,000 tons of diesel fuel into the nearby Ambarnaya River. Satellite images showed large swaths of the waterway contaminated from the spill.

Norilsk Nickel, the parent company of the plant, believes the region’s melting permafrost caused a reservoir to collapse, touching off the leak. Permafrost thawing across Siberia, linked to climate change, has caused widespread problems such as buckled roads, collapsed homes and disruptions to traditional herding and agriculture.

Russia’s branch of the environmental group Greenpeace described the spill as the largest in the Russian Arctic’s history, comparing it to the much larger Exxon Valdez oil spill of 1989 off Alaska in terms of potential environmental damage. The cleanup in the Arctic could cost more than $86 million, Greenpeace estimated.

The station’s employees originally tried to contain the leak on their own and did not report the incident to emergency services for two days, Yevgeny Zinichev, head of the Emergency Situations Ministry, said Wednesday during a nationally televised meeting chaired by Putin.

The governor of the Krasnoyarsk region, Alexander Uss, told Putin that he became aware of the oil spill Sunday after “alarming information appeared in social media.”

Putin then snapped at Sergei Lipin, the head of the subsidiary that owns the power plant, Norilsk-Taimyr Energy.

“Are we going to learn about emergency situations from social media?” he said.

Lakes and waterways more than 12 miles from the site contained concentrations of petroleum products that were tens of thousands of times higher than the maximum permissible limit, according to Russia’s regulatory agency for natural resources.

Lipin told Putin: “In line with the plan, this information was reported.”

“Was it really?” Putin responded. “Well, okay. I’ll have to ask the relevant monitoring and law enforcement agencies to find out what kind of information was reported where and what the response was from all those who are supposed to act accordingly in line with instructions.”

The Russian Investigative Committee said it has launched a criminal case over the pollution and alleged negligence. The power plant’s director, Vyacheslav Starostin, was taken into custody Thursday until July 31, but he has not yet been charged.

This was not the first spill for Norilsk Nickel, the world’s leading producer of nickel and palladium. In 2016, an accident at another one of its plants spewed oil into a nearby river. The industrial city of around 175,000 people, for whom Norilsk Nickel is the main employer, is considered one of Russia’s most polluted.

It is also in a part of Siberia that has experienced abnormally warm temperatures for this time of year — average temperatures since January are running at least 5.4 degrees above the long-term average, according to the U.S. National Oceanic and Atmospheric Administration.

Siberia, together with the Arctic as a whole, is warming at a much faster rate than other regions due to feedback that serves to hasten warming. This is raising concerns about its melting permafrost, which Sergey Dyachenko, Norilsk Nickel’s chief operating officer, pointed to as the cause for last week’s spill.

The current infrastructure present in the Arctic was constructed on the assumption that permafrost would, as its name suggests, be permanent. Thawing permafrost can destabilize structures, with giant holes already opening up in Siberia due in part to the thaw there.

A study published in Nature Communications in 2018 found that 45 percent of the hydrocarbon extraction fields in the Russian Arctic is located in areas “where thaw-related ground instability can cause severe damage to the built environment,” though it projected the worst impacts to unfold by mid-century.

Cleanup efforts for the Norilsk spill are expected to be especially tricky with the Ambarnaya River’s remote location. There are no roads, and it’s too shallow to use barges. Dyachenko told reporters Thursday that the company plans “to transport contaminated oil to temporary sites for remediation.”

Containment booms have been placed on the river to prevent oil from spreading further, but Greenpeace said on its website that they “will help collect only a minor part of the pollution, and therefore it would be safe to say that nearly all of the diesel fuel will remain in the environment.”

Uss, the region’s governor, told Putin on Wednesday that he could not make predictions about how long cleanup might take.

“What exactly will be done? You’re the governor, after all,” Putin said.

Andrew Freedman in Washington contributed to this report.