The death toll from a Colombian bus fire has risen to 32 after a boy hospitalised with severe burns succumbed to his injuries, authorities say.

Antonio Jose Pabon, who suffered burns over 95 per cent of his body and multiple organ failure, died on Thursday, Alma Solano, top health official in the city of Barranquilla, told AFP.

The seven-year-old was on board an overcrowded bus that burst into flames and exploded on Sunday in the small northern town of Fundacion as it was ferrying children home from church services.

The inferno is being blamed on the driver who, according to witnesses, set off the blaze when he tried to refuel the vehicle from a jerrycan.

Trapped inside, most of the bus’ young passengers burned to death.