JAKARTA, Indonesia — A passenger bus collided head-on with a fuel tanker truck on a highway on Indonesia’s Sumatra island on Wednesday, killing at least 16 people and injuring four others, officials said.

The crash occurred around midday on the Trans-Sumatra Highway in North Musi Rawas regency of South Sumatra province, when an intercity bus carrying at least 20 people struck a tanker truck traveling in the opposite direction, said Mugono, a local disaster management agency official.

Mugono, who uses a single name like many Indonesians, said preliminary findings indicate the bus — which was traveling from South Sumatra’s Lubuklinggau city to Jambi, another city — may have emitted sparks shortly before the collision. This may have prompted the driver to steer the vehicle toward the right side of the road in an attempt to avoid a more serious incident. However, an oil tanker truck was approaching at high speed, leaving little time to avoid a direct impact.

“The forceful impact triggered a fire that engulfed both vehicles, leaving many victims trapped inside,” Mugono said.

The dead include the bus driver and 13 passengers as well as the tanker’s driver and assistant, all of whom burned to death inside the vehicles, Mugono said.

Four bus passengers survived the crash and were taken to a nearby health clinic, including three who suffered severe burn injuries and one who sustained minor injuries, Mugono said.

As the passenger manifest is still being traced, Mugono said authorities are still collecting data on the total number of fatalities.

Photos and videos released by the National Search and Rescue Agency showed firefighters battling the blaze while thick plumes of black smoke and orange flames rose into the air. On the ground were the charred remains of the bus and tanker truck, with twisted metal scattered across the highway.

Rescuers, including disaster officers and traffic police, evacuated victims and cleared the wreckage, though several were pinned inside the vehicles, complicating rescue efforts and disrupting traffic along the highway, Margono said.

Road accidents are common in Indonesia due to poor safety standards and infrastructure.

Last week, a long-distance train slammed into a commuter train that had stopped near a station just outside the capital of Jakarta, after hitting a taxi that had broken down in the middle of the tracks. The collision killed at least 15 females of passenger sitting in the rear care, an area designated for women only.