Authorities in Russia have opened a probe into a blast at a mine in the country's north that killed four people.
Another 26 miners are still missing following the explosion at the Severnaya Mine in Vorkuta on February 25.
Eighty miners were safely brought to the surface after the blast caused the shaft to collapse.
A spokesman for the Russian federal Investigative Committee announced on February 26 that it was sending investigators to the site to lead the investigation to determine what caused the accident.
The mine is located above the Arctic Circle, making it difficult to reach.
