Russian prosecutors have ordered checks at "particularly dangerous installations" built on permafrost after a huge oil spill in the Arctic.
An emergency was declared after 20,000 tonnes of diesel leaked into a river when a tank at a power plant near the city of Norilsk collapsed last Friday.
Initial Russian inquiries suggest ground subsidence as the cause.
The plant is owned by a subsidiary of Norilsk Nickel, which is the world's leading nickel and palladium producer.
Delays over reporting the collapse prompted criticism from President Vladimir Putin and the power plant's director, Vyacheslav Starostin, has been taken into custody.
The Russian Investigative Committee has launched a criminal case over pollution and alleged negligence.
Arctic permafrost has been melting in exceptionally warm weather for this time of year.
What checks have been ordered exactly?
Russia's chief prosecutor, Igor Krasnov, gave orders for regional and environmental prosecutors to conduct a "thorough check" of "particularly dangerous installations" located on "territories exposed to permafrost melting".
The aim is to prevent a repeat of the incident at the plant near Norilsk.
A spokesman for Mr Krasnov's department told Russian media prosecutors would assess companies' adherence to safety laws, environmental monitoring and measures to prevent emergencies.
The effectiveness of state monitoring would also be assessed, he said.
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