PALU, Indonesia (AP) — A smelting furnace exploded Sunday at a Chinese-owned nickel plant on Indonesia’s Sulawesi island, killing at least 13 workers and injuring dozens of others, police and a company official said.

It was the latest of a series of deadly accidents at nickel smelting plants in Indonesia that are part of China’s ambitious transnational development program known as the Belt and Road Initiative.

Nickel is a key component in global battery production for electric vehicles.

At least five Chinese and eight Indonesian workers died when the furnace suddenly exploded while they were repairing it, said Central Sulawesi police chief Agus Nugroho.

The blast was so powerful it demolished the furnace and damaged parts of the side walls of the building, said Nugroho, adding that about 38 workers were hospitalized, some in critical condition.

Authorities are working to determine whether negligence by the company led to the deaths, Nugroho said.

The accident occurred at PT Indonesia Tsingshan Stainless Steel, a subsidiary of PT Indonesia Morowali Industrial Park, known as PT IMIP, in the Bahodopi neighborhood of Morowali regency.

“We sincerely apologize for this incident and we are working closely with authorities to investigate what caused the accident,” said company spokesperson Deddy Kurniawan.

Rescuers extinguished the fire and evacuated workers after a nearly four-hour operation, he added.

A preliminary investigation showed there were explosive liquids at the bottom of the furnace that triggered a fire and explosion in nearby oxygen cylinders.

It was the third deadly accident this year at Chinese-owned nickel smelting plants in Central Sulawesi province, which has the largest nickel reserves in Indonesia.

Two dump truck operators were killed when they were engulfed by a wall of black sludge-like material following the collapse of a nickel waste disposal site in April.

In January, two workers, including a Chinese national, were killed in riots that involved workers and security guards at a Indonesia-China joint venture in North Morowali regency.

Last year, a loader truck ran over and killed a Chinese worker while he was repairing a road in PT IMIP’s mining area, and an Indonesian man burned to death when a furnace in the company’s factory exploded.

Nearly 50% of PT IMIP’s shares are owned by a Chinese holding company, and the rest are owned by two Indonesian companies. It began smelter operations in 2013 and is now the largest nickel-based industrial area in Indonesia.

Three Chinese workers last month filed a complaint to Indonesia’s National Commission on Human Rights, alleging that their health is deteriorating due to dust and smoke exposure while working seven-day weeks without a break at PT IMIP. They added that workers there don’t have adequate safety equipment.

Data collected by the Mining Advocacy Network, an Indonesian watchdog, showed that at least 22 workers from China and Indonesia have died in nickel smelting plants in Central Sulawesi province since 2019, including two Chinese nationals who committed suicide.