Colombian authorities have arrested the driver of a bus that crashed and killed 31 children, police said Monday.
The youngsters burned to death Sunday after the bus caught fire and exploded in the north of the South American country as they returned from church services.
Another 25 people -- including one adult -- were injured and seriously burned in the blaze at the town of Fundacion, in the department of Magdalena, according to the Red Cross.
"The driver has been arrested, he turned himself in to authorities and we expect him to explain himself at a hearing this morning," a local police spokesman told AFP.
The driver had initially fled the scene, and angry locals went to his home and threw rocks at his windows.
Investigators are looking into a number of potential causes of the crash, which prompted President Manuel Santos to travel to the scene and offer his condolences.
Among the possibilities being explored is that the driver used contraband gas to refuel the bus and that this may have led to the explosion.
Other theories being explored is that mechanical failure is to blame.
Red Cross official Cesar Uruena said Sunday the injured -- taken to area hospitals -- suffered second and third-degree burns, and many were in critical condition.
The children aboard the bus were between the ages of one and eight and were returning home after a religious service, Fundacion Mayor Luz Stella Duran told reporters.
Magdalena police told AFP that the bus exploded around noon, and that the fire was so intense they had problems determining the number of casualties.
Duran said survivors reported that the bus driver had been handling a container with gasoline aboard the vehicle. Police initially blamed the fire on a mechanical problem.
Santos traveled to Fundacion after a final re-election campaign rally Sunday in Bogota ahead of the May 25 presidential vote.
"The entire country is in mourning for the death of these children," Santos said upon arriving in Fundacion, accompanied by his wife.
Santos said the government would pay for all hospital and funeral expenses relating to the accident.
The bus, which was being used by an evangelical church group, caught fire one block away from the church where the children had earlier attended services.
The Red Cross said it was sending four psychologists and two volunteer specialists to help the wounded and the relatives of those killed.