At least 30 people died on Friday in a fire that swept through a small factory producing matchsticks in Indonesia’s North Sumatra province, authorities said.

The fire broke out at midday in the makeshift facility in a residential area, killing 27 adults and three children, said Riadil Akhir Lubis, head of the provincial disaster mitigation agency.

Police are investigating the cause of the fire, he said.

“[The children] were probably not workers. Their parents, who lived nearby, brought them to work,” Irwan Syahri, head of the local disaster agency, told Metro TV.

A video circulated on social media showed emergency workers inspecting the site and what appeared to be charred bodies in the ruins.

Indonesia has a patchy industrial safety record. In 2017, a series of explosions and a fire killed 47 workers and injured dozens at a fireworks factory on the outskirts of Jakarta.