About 60 people were killed and dozens more wounded on Monday in an explosion at an informal gold mining site in southwest Burkina Faso, state television reported, citing local officials.

The cause of the explosion in Poni province was not yet known, Poni’s high commissioner Antoine Douamba told state television.

Images showed a large blast site of felled trees and destroyed tin houses. Bodies lay on the ground, covered in mats.

It was not clear exactly what kind of gold mining went on at the site. Burkina Faso is home to some major gold mines run by international companies, but also to hundreds of smaller, informal sites that operate without oversight or regulation.

Children frequently work in these so-called artisanal mines; accidents are common.

Burkina Faso, one of the world’s least developed countries, is under attack from Islamist groups linked to al Qaeda and Islamic State who seek control of mining sites as a means to fund their violent attacks.

Monday’s blast was hundreds of miles from where these groups usually operate and there was no sign that Islamist militants were involved.