A national day of mourning has been declared in Colombia to honour 32 children who were burned alive when the bus they were travelling in caught fire.

President Juan Manuel Santos interrupted campaigning ahead of May 25 elections and travelled to Fundacion, where the blaze happened, to pay his respects to the victims.

Speaking to the children's families, he said: 'We are with you, the whole country is with you.'

The children, who were being ferried home from Sunday school, died after the bus driver allegedly tried to refuel the vehicle from a jerrycan and the petrol caught fire.

 

The infants, who were aged three to 12, died after becoming trapped inside the bus. Around 20 more were taken to hospital in a 'delicate state', according to the mayor of Fundacion, Luz Estella Duran.

The driver and the evangelical pastor who chartered the bus face prosecution for 'voluntary homicide so that public prosecutors can request the maximum penalty' of up to 60 years, attorney Mauricio Ramirez said.

His defense lawyer is challenging the murder charge, asking instead for a charge of involuntary homicide, which carries a maximum penalty of 15 years.

'This was negligent conduct but not intentional. We cannot compare them to criminals who intended to do harm,' another attorney for the suspects, Diego Duque, said. 

'He made a mistake but one cannot say it was deliberate,' Duque said, adding that one of the driver's daughters died in the fire.  

Nelson Tapias, a 54-year-old merchant in the town, said he lost his granddaughter and several nephews. He said: 'I have my heart torn apart in six pieces.'

Bus accidents are frequent in Colombia, especially in poorer, rural areas like the one near Fundacion where inspections and transport laws are rarely enforced.

Gen. Carlos Mena, the highway police commander overseeing operations in Fundacion, said the driver was operating the bus without a license or insurance. 

The 1993 Dodge's registration papers were also out of date and the bus was carrying twice the maximum number of passengers allowed.

Authorities would not say where the driver was being held, for fear he could be harmed by outraged residents in the rural town of 80,000 people.

The whereabouts of the pastor, Roberto Padilla, was also unknown.

'Last night they wanted to burn him alive, so for his own safety they removed him from the town,' said Fanny Valseiro, who has been attending services at the church for more than a decade.

Padilla, in a radio interview from an undisclosed location, said that the he and the rest of the church leadership were unaware of the bus driver's violations.

Prosecutors said late Monday that they also planned to press charges against Manuel Ibarra, a member of the congregation who was responsible for contracting the bus.