Gas Explosion Death Toll Rises

Gas explosions inside mines are often caused when a flame or electrical spark ignites gas leaking from the coal seam.

Chinese state media says 33 coal miners trapped underground during a gas explosion have been found dead, as work safety officials vowed to punish those responsible.

Key points:

33 people dead, Xinhua reports might change

Two survived the gas explosion

China is the world's largest coal producer

Two miners survived Monday's explosion but rescuers working around the clock found no others alive.

All bodies have been recovered and rescuers were shown bowing their heads in memorial for the dead.

Ventilation systems are supposed to prevent gas from becoming trapped.

The State Administration of Work Safety ordered an investigation into the blast, adding that "those responsible must be strictly punished".

Local officials in Chongqing, where the incident happened, also ordered smaller mines to shut down temporarily, Xinhua said.

China's mining industry has long been among the world's deadliest.

The head of the State Administration of Work Safety said earlier this year that struggling coal mines might be likely to overlook maintenance.

China is the world's largest producer and consumer of coal but plans to shutter more than 1,000 outdated mines as part of a broader plan to reduce overproduction.

AP