Authorities in Bangladesh struggled Monday to determine the cause of a devastating fire that killed at least 41 people, including nine firefighters, and injured more than 100 others at a shipping container storage depot, as experts raised concerns over the country’s industrial safety standards.

Efforts to fully extinguish the fire at the BM Inland Container Depot, a Dutch-Bangladesh joint venture near the country’s main Chittagong Seaport, continued Monday after it broke out around midnight Saturday following explosions in a container full of chemicals. The explosions were felt as far as 4 kilometers (2 1/2 miles) away, officials and local media said.

Authorities said there were more than 4,000 containers at the depot, of which about 1,000 were filled with materials including chemicals.

Nearly 40 hours after the initial explosion, smoke was still coming out of some containers. Explosives experts from the military were called in to assist the firefighters.