The bodies of at least 16 people have been found in the burnt-out shell of a bus on a rural road in eastern Guatemala, police officers say.
Initial reports suggested the victims were local farm workers but Guatemalan media reports said the bus and its passengers had come from Nicaragua.
Authorities say they have not ruled out an intentional attack.
The fire happened in the Zacapa area, some 140km (87 miles) from the capital, where drug gangs are known to operate.
Police said the people on board the bus were found still in their seats, their bodies so badly burned that even their gender could not be initially established.
The identitity of those on board is still unclear but Guatemalan media report that a bus had set off from Nicaragua on Friday heading for Guatemala City.
Contact was lost late on Saturday with the vehicle which never arrived at its destination
Authorities have not ruled out the possibility that the fire was set intentionally.
Police officers said traces of petrol had been found on and around the bus.