QUETTA, Pakistan (Reuters) - At least 16 miners died on Saturday and more than a dozen others remained trapped after an explosion in a coalmine in southwest Pakistan, officials said.

The blast in the Marwar coalfields in Baluchistan province was caused by a build-up of methane gas inside the mine, Director of Disaster Management Attaullah Khan said.

“We have retrieved 11 bodies”, Khan said, adding five others were still in the mine.

Efforts to rescue the trapped miners were under way, Chief Inspector of Mines Iftikhar Ahmad said. He said two other laborers died in a landslide in an another mine nearby. It was not immediately clear if that was caused by the explosion.

Accidents are frequent in the province’s mines, where safety measures are basic and much of whose workforce is drawn from laborers from other parts of Pakistan.

The mines are mostly owned by state-run Pakistan Mineral Development Corporation, which leases many of them to private contractors.

The country has huge coal reserves estimated at more than 184 billion tonnes. It produces 4 million tonnes of coal annually, most of which is consumed by brick-making kilns.

The Marwar coalfields lie some 60 km (35 miles) east of Baluchistan’s capital Quetta.