The overcrowded bus was picking up attendees at an event in Fundacion, in northern Colombia,
when the fire began, Col. Adam Leon said, adding that some children escaped and that authorities are investigating the cause of the fire.
"Everyone started to scream and run," a child survivor said of the incident.
The adult victim was Harry Aaron, a civil defense official in the Magdalena municipality.
A witness said the driver left the scene to get a drink, and children were charged with putting gasoline into the tank of the vehicle.
Colombia President Juan Manuel Santos, who was in northern Colombia at the time, traveled to Magdalena to offer condolences to victims.