A head-on collision between a bus and a car in mountains on the Myanmar-Thai border killed 19 and left more than 30 injured on Friday.
Images posted by local media showed the bus upside down after it span off the road and plummeted down a steep bank at a spot notorious for traffic accidents.
Myanmar Social Rescue Group vice-chairman Aung Myint told AFP the express bus had been travelling from Yangon Friday morning when it careered into an oncoming car after its brakes failed.
"The bus plunged off the mountain, killing 18 and injuring 33 outright," he said by phone, adding the number included the car's seven passengers who all lost their lives.
A doctor at Myawady hospital confirmed that one critically-injured woman later died, bringing the toll to 19.
Myawady town in Karen state is one of the key land border points between Myanmar and Thailand with hundreds of traders crossing daily in both directions.
"A lot of accidents happen here," Aung Myint said about the site of the accident, where the highway comprises a series of steep switchbacks as it cuts through the thickly-forested mountain range.
Myanmar's road safety standards lag behind neighbours in the region and crashes are common.
An accident last week in neighbouring Mon state killed 10 people while 15 pilgrims returning from a Buddhist festival in October died when their truck plunged from a cliff in Shan state to the north.