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major mine explosion near Sawahlunto city, West Sumatra, Tuesday, killed at least nine people while more than 30 were buried and are feared dead, officials said.

Rescuers were trying to reach those trapped underground.

By 6 p.m., at least nine bodies were recovered after the morning explosion at the 100-meter-deep mine at the hilly Bukit Bual area, some 100 kilometers from the provincial capital of Padang, and seven of them have been identified, they added.

Rescuers used excavators and wind blowers, and wore masks to dig into the underground blast site in search of dozens of victims.

Health Ministry Crisis Center chief Rustam Pakaya said 14 miners were rescued, but five with severe burns died later in a hospital.

Two others were in critical condition, he told AP.

Sawahlunto mayor Amran Nur said that based on preliminary questioning of survivors, some said 24 workers were inside the mining site, while others said there were at least 30 miners trapped underground.

"The attendance sheet was also burned, so the number of buried victims is still not certain - approximately between 24 and 30 people," he told The Jakarta Post in Padang after returning from the blast scene.

Amran said there was a "very slim chance" that any buried victims were still alive because they would be very short of oxygen underground.

The blast site contained excessive methane gas, the mayor added.

Authorities were still investigating the cause of the explosion.

A preliminary probe indicated that the methane gas blast may have been triggered by a short circuit.

"The explosion reached 100 meters high into the mining crater, leaving eight people there also burned," Amran said.

He said the mining site was actually under control of the private firm PT Datras which had obtained its mining permit from the Sawahlunto administration.

But the mine was managed "illegally" by local people, he added. "They had often been reprimanded about dangers as they mined without adequate safety standards."

In Jakarta, Bambang Setiawan, director general of coal, minerals and geothermal at the Energy and Mineral Resources Ministry, said the devastated coal mine was operating under mining concessions issued by the regional administration.

He said the local government was supposed to supervise closely the mining activities in Sawahlunto. "Sometimes, the mining permit is so easily granted, but further assistance and supervision about good mining practices are often forgotten," he said.

"Underground mining is not easy. It requires advanced technology, including heavy machinery. Even in surface mining, landslides can still occur if you mine the wrong way," Bambang said.