The spectacular crash occurred on Saturday around 9.50pm near Züberwangen under circumstances that remain under investigation.
The driver of a silver BMW died in the vehicle after it collided with the Peugeot camper van, while two passengers, men aged 25 and 31, were flown by two Rega (emergency rescue) helicopters to hospital for treatment of severe burns, St. Gallen cantonal police said in a release.
The 46-year-old male driver and a 47-year-old female passenger escaped with slight injuries from the burning vehicle, police said.
Emergency rescue officials arriving at the scene saw possessions from the van, which was on fire, spilled along an area of 100 metres.
The burning BMW was on its roof and the driver died on the spot, police said
“The burns caused by the fire have not yet allowed the identification of the deceased driver,” Hanspeter Krusi, spokesman for the St. Gallen cantonal police force is quoted as saying by Le Matin newspaper online.
Investigators are still trying to determine the identity of the man who died, police said.
The accident led to the closure of the A1 motorway between Oberbüren and Wil for five hours.
More than 70 emergency workers responded to the crash, including 50 local fire fighters, three ambulances, two helicopters, medical attendants and several police patrols.
Police are seeking witnesses to shed more light on the causes of the collision.
Anyone with possible information is asked to phone 058 229 81 00.