An explosion in a coal mine in Russia's Arctic killed seven people and left three missing, the Emergency Situations Ministry said Tuesday.

The blast hit the Komsomolskaya mine in Vorkuta, about 1,200 miles northeast of Moscow, on Monday evening. There were 277 people in the mine at the time, the ministry said in a statement.

Most were able to reach the surface on their own, but four were hospitalized with injuries of unspecified severity, the statement said.

The ministry said the explosion apparently was due to methane, but it was not clear what ignited the gas.

Russia has seen a series of mine accidents and disasters this year that have highlighted the hazardous state of the country's mines.

A methane blast at a Siberian coal mine that killed 39 miners in May was blamed on interference with a safety system. A methane blast in March that killed 110 workers at a nearby mine was Russia's worst coal mining accident in more than 60 years.