The driver turned himself over to police as families sought to hunt him down following Sunday's tragedy in which, according to a witness, the bus went up in flames as he refuelled it with a jerrycan.
The children, aged between three and 12, were returning from evangelical church services in the small northern town of Fundacion. The driver lost two of his own children in the fire.
Fundacion Mayor Luz Stella Duran said another 20 were hospitalised. Most of the injured have second- or third-degree burns.
Residents of the town had raced to join firefighters to extinguish the raging blaze, but it was too late.
"We wanted to get out a young girl who was holding out her arms by a window, but her skin was peeling off," witness Jose Guette, 48, said.
"We couldn't do anything but hold our heads and watch the children burn."
Yesterday, bamboo crosses were erected along the road where the bus burned, and glass fragments were still scattered on the ground. A woman was on her knees on the asphalt, wailing.
The mayor has declared three days of mourning and banned alcohol consumption.
President Juan Manuel Santos, who rushed to the scene, said an investigation was under way, while many denounced the accident as an example of Colombia's poor enforcement of road safety.
"I am shattered and the whole country is in mourning for the death of these children in this tragedy. We will never forget them," the president said.
Crews pulled small charred bodies from the wreckage and took them to the medical examiner's office in the regional capital of Barranquilla to be identified -- a task which could take days.
The driver gave himself up to police after townspeople hurled rocks at his home. He was due to appear at court to explain how the tragedy unfolded.
The prosecutor's office said the driver lacked a license to drive and will be charged with aggravated manslaughter, as will Manuel Ibarro, a member of the church that hired the bus.
Transport Minister Cecilia Alvarez said the vehicle had lacked the authorisation to provide services since 2012.