The death toll from a massive explosion in an Indonesian coal mine has risen to 27, with around a dozen men still trapped and feared dead deep underground, officials say.

Rescuers today pulled another 10 bodies from deep within the mine in West Sumatra province, which collapsed after an explosion of methane gas on Tuesday, health ministry crisis centre head Rustam Pakaya told AFP.

"The bodies were found inside the mine around 150 metres down," Pakaya said.

The accident left nine people injured in hospital, while around a dozen were believed to be still trapped underground, provincial disaster management chief Ade Edward said.

"There's a large chance that they're already dead because there's a lot of carbon dioxide there," he said.

The blast at the mine in Sawah Lunto district sent flames 50m into the air and left a huge crater on the surface, officials have said. Miners were using traditional methods with few modern safety measures in place.

Disaster response official Adriyusman said a dangerous concentration of methane was hampering rescue efforts. "If we look at those that have been taken out I don't think it's likely (the others survived). It's up to God's will," he said.

Accidents are common at Indonesian mines, especially at illegal digs with no safety precautions, industry sources said.

A gas drilling operation linked to one of the country's biggest conglomerates allegedly triggered a massive mud volcano on Java in 2006, killing 13 and displacing some 40,000 people.

Indonesia has the largest coal reserves in the Asia-Pacific region behind Australia, India and China, according to the World Coal Institute. It is the world's second largest coal exporter after Australia.