Death toll from the deadly coal mine blast in northeast China's Heilongjiang Province has risen to 87 as of 7 a.m. Sunday, said local authorities.

Another 21 are still trapped in the shaft.

The blast happened at around 2:30 a.m. Saturday at the Xinxing Coal Mine under the state-owned Heilongjiang Longmei Mining Holding Group's subsidiary in Hegang City. A total of 528 miners were working underground, among whom 420 have escaped the accident, said staff with the company.

More than 240 rescuers in 19 group have been sent into the shaft, while more than 300 others were helping with the rescue work, said Zhang Zhenlong, assistant chief engineer of the subsidiary.

"The blast didn't result in much damage to the laneways, but it crippled the ventilation system and communication facilities," Zhang said, adding that the rescue work in the past a few hours was to repair the ventilation system.

"Fresh air from the outside could add more chances for survival of the trapped miners."

Li Zhanshu, governor of Heilongjiang, ordered more efforts in management of coal mines.

"We must put safety first," he said. "Development is important, but the growth of GDP shouldn't be achieved at the price of miners' blood."