Beijing, Nov 23 (DPA) The death toll from a gas explosion at a coal mine in north-eastern China has risen to 104, with four workers still trapped underground, state media said Monday.

The explosion occurred early Saturday in the Xinxing mine in Hegang City, Heilongjiang province, as 528 miners were working underground.

By early Monday morning, rescuers had found 104 bodies, 420 workers had escaped and four others were still missing, the official Xinhua news agency reported.

More than 100 rescue teams were working at the site, and operations were being overseen by China’s vice premier, Zhang Dejiang, earlier reports said.

At the time of the explosion, an evacuation was underway due to a warning about gas levels in the shaft, according to state broadcaster, CCTV.

The blast came as the government is trying to reform China’s notoriously dangerous mining industry, by closing illegal operations and reducing the number of small and medium-sized mines through mergers.

While the illegal, and small and medium-sized mines, have high production output, they also have poor safety and environmental records.

Saturday’s accident was also a reminder of ongoing safety concerns at even large state-owned mines.

An investigation into the cause of the gas explosion was being led by the chief of China’s State Administration of Work Safety Luo Lin.

China’s official mining death toll was 3,215 last year, but industry analysts suspect the actual figure to be higher.