This aerial picture shows a general view of Indonesia Morowali Industrial Park in Konawe Utara. AFP

At least 13 people were killed and 38 injured in eastern Indonesia on Sunday in an explosion at a Chinese-funded nickel-processing plant, the owner of the industrial park that hosts the facility said.

The island of Sulawesi is a hub for the mineral-rich country's production of nickel, a base metal used for electric vehicle batteries and stainless steel, and Beijing's growing investment has stoked unrest over working conditions at its facilities.

The accident occurred around 5:30 am (2130 GMT Saturday) at a plant owned by PT Indonesia Tsingshan Stainless Steel (ITSS) in the Morowali Industrial Park in Central Sulawesi province, a spokesperson for the complex said in a statement.

"(The death toll) increased by one person, from 12 to 13," he told AFP, also revising the number of injured down one to 38.

He identified the dead as eight Indonesians and five Chinese workers.

An initial investigation showed the explosion happened during repair work on a furnace when a flammable liquid ignited and the subsequent blast caused nearby oxygen tanks to explode as well, the official said.

The fire was extinguished Sunday morning, according to the statement.

Tsingshan Holding Group, the world's biggest nickel producer and China's biggest stainless steelmaker, holds a majority stake in ITSS.

ITSS is a tenant in the industrial park, which is also majority owned by Tsingshan along with local partner Bintang Delapan.

Agence France-Presse