KIEV, April 17 (Xinhua) -- Seven workers were injured in a coal mine blast in Ukraine's eastern Donetsk region on midnight Monday, authorities said.

A mixture of methane and air exploded in the "Pokrovskaya" mine at a depth of 470 meters, when 406 miners were working underground, the State Emergency Service said in a statement.

According to the statement, rescuers evacuated the trapped miners to the surface within an hour, and the injured have been taken to a hospital.

One of the injured is in grave condition, according to authorities.

The blast was the second accident in "Pokrovskaya" mine this year. Eight miners were injured in a methane gas explosion inside the mine in January.

Twenty-three people died and 757 others were injured in coal mine accidents in Ukraine last year.