A major Ukrainian drone attack on Russia triggered a giant blast and forced the partial evacuation of residents near the site of a large Russian arsenal in the Tver region on Wednesday, war bloggers and some media reported.

Unverified video and images on social media showed a huge ball of flame blasting high into the night sky and detonations thundering across a lake in the region that lies northwest of Moscow and not far from the border with Belarus.

NASA satellites picked up several sources emanating from the site in early Wednesday hours and earthquake monitoring stations picked up what sensors thought was a minor earthquake in the area.

Fire fighters were trying to contain the fire, Igor Rudenya, the governor of the Tver region, said in a post on the Telegram messaging channel of the region’s administration. He did not say what was burning.

According to an RIA state news agency report from 2018, Russia was building an arsenal for the storage of missiles, ammunition and explosives in Toropets, a 1,000-year-old town, which has a population of just over 11,000.

Russian state media had suggested it was a major arsenal for conventional weapons.

There was no information about casualties.

The size of the main blast shown in the unverified social media video was consistent with 200-240 tons of high explosives detonating, according to George William Herbert of the Middlebury Institute of International Studies at Monterey in California.

Reuters was unable to immediately confirm that what state media had reported was a major arsenal had been hit. The defence ministry did not respond to a request for comment.

Schools and kindergartens were moved online in the Zapadnodvinsky district, which borders the Toropetsky district, the administration of the district said on the social VKontakte network.

Russia’s air defence units destroyed 54 drones that Ukraine launched overnight against five western Russian regions, Russian state news agencies cited a report from the Russian defence ministry as saying.

Regional governors reported no damages from those attacks.

But the defence ministry report did not mention the Tver region, which borders the Moscow region to its southeast.

Reuters could not independently verify the reports. There was no immediate comment from Ukraine.

Kyiv has previously said its strikes on Russia are aimed at military, energy and transport infrastructure key to Moscow’s war efforts.

Russian officials rarely disclose the full extent of damage inflicted by Ukrainian attacks.

As Ukraine has ramped up its domestic drone production over the past two years, it has increased attacks on Russian territory.

Ukraine’s biggest-ever drone attack struck the Russian capital in September, killing at least one, wrecking homes and disrupting flights at Moscow’s airports.