QUETTA, Pakistan (AP) — A methane gas explosion killed six coal-miners overnight in southwestern Baluchistan province, near the Afghan border, Pakistani authorities said Friday.

Naseer Nasir, a mine inspector, said the blast was cause by a buildup of the gas inside the mine in the town of Marwar, some 50 kilometers (30 miles) east of Quetta, Baluchistan’s capital city.

Two miners were also injured, he said, adding that a search and rescue operation had completed, but that investigators were still working to determine the cause of the explosion.

Safety standards are commonly ignored in the coal mining industry in Pakistan, leading to accidents and explosions that have killed numerous miners in recent years.