A footwear factory fire in the Philippines killed 72 workers last week, many of whom were trapped on the second floor of the building, investigators said. The fire happened last Wednesday at a rubber slipper factory in Valenzuela City, near the capital of Manila. The factory is owned by the Kentex Manufacturing Corp., which sells flip-flops under the brand name Havana. “The situation happened very fast,” said Rhay R. Sousa, a city spokesperson. “Some people had to jump from the building to escape.”

Investigators have not released an official cause of the fire, although initial reports indicate the blaze may have been set off from welding work on the factory’s gate. It appears sparks ignited chemicals contained in nearby containers. More than three dozen officers from the Philippine National Police’s forensic examination team have joined the evidence recovery process.

“Someone will definitely be charged because of the deaths,” said police Deputy Director General Leonardo Espina. “It doesn’t matter if it’s an accident, people died. Many of those retrieved were reduced to skulls and bones.”

Since the fire, labor activists have staged protests in Manila, demanding an investigation of the factory owners. The protestors have specifically questioned whether the factory had been properly inspected and if the facility had enough fire exits and fire extinguishers. Reports suggest Kentex was compliant with safety requirements as of September of 2014, its latest inspection date.

The fire was one of the most deadly in Philippine history. In 1996, 162 people died in a disco club fire in a suburb of Manila. In 2001, a hotel fire in Quezon City killed 75 people.