XI'AN, Jan. 14 (Xinhua) -- Six people have been detained in northwest China's Shaanxi Province after a coal mine collapsed and killed 21 miners.

A legal representative for Baiji Mining Co. Ltd, which owns the coal mine in Shenmu, the head and four other associates of the coal mine are under criminal detention, Shenmu police said.

The roof of the coal mine, Lijiagou Colliery, collapsed on Saturday afternoon. Twenty one out of 87 miners who were working under ground were trapped and died, the local police said.

The company's bank accounts have been frozen, the police said.

An investigation into the accident is underway.