At least 20 people were killed in Thailand on Friday morning when the bus they were on caught fire, Reuters reported. The bus was carrying 47 migrant workers from Myanmar to Bangkok. Three people sustained serious injuries in the blaze.

The accident took place at 1.25 am in Tak province which borders Myanmar. The driver said he saw the fire start from the middle of the bus and spread quickly, AP reported. People who were seated in the front of the vehicle managed to escape, but those in the back were trapped.

The cause of the fire has not yet been ascertained.

On March 21, a bus had slid off the road after losing control on a downhill curve in Thailand, killing 18 people. A day later, a school bus had skidded in the rain and flipped over in Ayutthaya province, injuring 39 people.

A recent study by the World Health Organisation ranked Thailand’s roads as the deadliest in the world after Libya’s, Reuters reported.