An explosion rocked a subway station Monday in the Russian city of St. Petersburg, and the Russian news agency Tass reported that several people were injured.

Evacuation is underway, and seven metro stations in the city have been closed following the blast, Tass said.

A spokesman for the regional department of Russia’s Emergencies Ministry told the news agency it was checking reports on the smoke in the metro. "There is a complaint about the smoke, the staff members are going to the scene," a police official said.