A Russian train carrying tanks of natural gas derailed and exploded Thursday in Pozdino in the Novovyatsky district of Kirov.
About a dozen of the tanks erupted into flames.
The explosions and fire forced the evacuation of at least 500 residents from the area.
Kirov is northeast of Moscow.
The acting governor of the Kirov Oblast region, Nikita Belykh, said testing teams are on site to monitor potential pollution but no toxins have been found in the local water supply, EuroNews said.
Emergency crews responding to the fire number about 250 people.
Fire-fighting trains and a helicopter services have been battling to contain the blaze.
The incident has delayed more than 10 passenger trains, including two international trains.
There have been no reports of casualties.