Nearly 20,000 tons of diesel fuel leaked into a river within the Arctic Circle in Russia, following the collapse of a fuel tank at a power plant. Russian President Vladimir Putin declared a state of emergency as environmental organizations warned over the impacts of the massive spill.

The accident happened on May 29 at the city of Norilsk, one of the world’s most polluted places due to its industrial activity. The oil leaked from a tank in a plant managed by a subsidiary of Norilsk Nickel, the world’s largest producer of palladium and one of the largest producers of nickel, platinum and copper.

“The accident took place at the industrial site of the Nadezhdinski Metallurgical Plant, and part of the spilled petrochemicals, a considerable amount actually, seeped into the Ambarnaya River,” Putin said as he discussed the incident with officials on Wednesday, according to the Kremlin

The region’s governor, Alexander Uss, had earlier told President Putin that he became aware of the oil spill on May 31st after “alarming information appeared in social media.” The two-day delay from the onset of the spillage led to Putin harshly criticize the head of the company.

“Why did government agencies only find out about this two days after the fact?” Putin asked the subsidiary’s chief, Sergei Lipin. “Are we going to learn about emergency situations from social media?” Putin has ordered an investigation into the accident. A manager at the power plant was arrested.

Nevertheless, the president’s claims were dismissed by the company responsible for the spill. Emergency teams were “immediately” sent after the accident to start to clean up, Norilsk Nickel said on its website – adding that the spill happened in a remote area and that no local community had been impacted.

“A regional emergency situation was declared in the city of Norilsk and Taymir region. An emergency response team was set up chaired by the city mayor of Norilsk,” the company said, claiming it was trying to limit damage to the local environment – a challenging task according to environmental organizations.

The second-largest environmental accident in modern Russian history

Alexei Knizhnikov, an expert from the World Wildlife Fund, told AFP that the accident is believed to be the second-largest in modern Russian history in terms of volume. Greenpeace has compared it to the 1989 Exxon Valdez disaster in Alaska and warned it will be difficult to clean it up due to its size and the geography of the river.

“There has never been such an accident in the Arctic zone,” said Oleg Mitvol, former deputy head of Russia’s environmental watchdog Rosprirodnadzor. According to Mitlov, the clean-up could cost about 100bn roubles ($1.5 billion) and take between five and 10 years.

Meanwhile, the government is looking for solutions. Russia’s minister of natural resources, Dmitry Kobylkin, dismissed the possibility of burning off the fuel oil due to its size, proposing instead to dilute the oil with reagents. He also suggested pumping the oil on to the adjacent tundra, something dismissed by Putin.