At least 18 miners were killed and more than a dozen were still trapped on Tuesday after a rockslide at a marble mine in northwest Pakistan, officials said.

Boulders of white marble came crashing down on workers on Monday evening in the mountainous Mohmand district in Khyber-Pakhtunkhwa province, near the border with Afghanistan.

“So far 18 bodies and 20 injured have been pulled out after a rockslide at a marble mine,” Muhammad Arif, the provincial minister for mines and minerals development, told AFP.

He said around 20 more miners were still believed to be trapped under the rubble with a rescue mission under way.

Labourers often rest at the bottom of the mountains after long working hours.

A senior official from Mohmand district, Hamid Iqbal, confirmed the death toll.

Pakistan’s mines are notorious for poor safety standards. Dozens of miners are killed each year in different safety-related incidents.

At least 43 miners were killed in Sorange district of Balochistan in 2011 as a result of a blast at a coal mine.