The number of people killed when a bus plunged into a ravine on Indonesia’s Sumatra island has risen to 28, police and rescuers have said, with 13 others injured.

The accident occurred just before midnight on Monday on a winding road in South Sumatra province’s Pagar Alam district when the bus’s brakes apparently malfunctioned.

Search and rescue operation chief Berty Kowaas from the province’s capital, Palembang, said the bodies were taken to a hospital for identification, including that of a young boy who was pulled from a river near the crash site.

One of the injured was in critical condition, local police chief Dolly Gumara said.

Gumara said the bus plunged into a 80 metre ravine and crashed into a fast-flowing river after the driver lost control of the vehicle in an area with a number of sharp declines.

Survivors told authorities that the vehicle’s brakes apparently malfunctioned, but police were still investigating the cause of the accident, Gumara said.

The bus was headed for Palembang from the neighbouring city of Bengkulu.

Kowaas said the search for other passengers who might have been dragged away by the river was halted as darkness fell and would be resumed on Wednesday morning.

The capacity of the bus was 52 passengers, but the number of passengers on board was unclear. The driver and two crew were among those killed.

Television footage showed police and rescuers from the national search and rescue agency evacuating injured victims and carrying the dead in blue body bags. Relatives waited for information about their loved ones at the bus company’s office in Bengkulu and at Pagar Alam’s Besemah hospital.

Road accidents are common in Indonesia because of poor safety standards and infrastructure.

Early last year, 27 people were killed when a packed tourist bus plunged from a hill in West Java province. Two months later, two accidents in the province’s hilly resort region of Puncak killed at least 15 people. In September last year, 21 were killed when a tourist bus plunged into a ravine in Bogor, another hilly area in West Java.