HARBIN - Police have arrested four people after a colliery explosion killed at least 21 in northeast China's Heilongjiang Province Tuesday, local authorities said Saturday.

Among the four suspects are the mine owner and three managers, the emergency rescue headquarters said in a statement.

The blast went off at Jingyou Coal Mine, a privately-owned pit in Qitaihe City, at 9 p.m. Tuesday. Of the 22 miners trapped, 21 were confirmed dead and one remained missing.

Rescuers retrieved the 21 dead bodies Friday night and are still searching for the missing miner.

A team of investigators are trying to find out the cause of the accident.