Four school students were killed Monday when the CNG cylinder of a van they were travelling in exploded in a north west suburb of Mumbai, police said.

The explosion took place in the Millat Nagar area of suburban Oshiwara on Monday afternoon, they said. "The children, all in the age group five to ten-years-old, are all from the Millat High School and had boarded the Omni van which was to take them home. When the van was started by the driver the CNG kit exploded killing three girls instantly," they said.

The three who died sustained 100 per cent burns, while one of the children was declared dead after being taken to a local hospital. There were 11 children travelling in the van and many of them have sustained serious burn injuries after the van caught fire following the explosion, they said.

All the seven injured children have been taken to the nearby Cooper hospital where they are undergoing medical treatment. "The driver of the vehicle managed to escape uninjured and has been detained," a senior police official from the Oshiwara police station told PTI.

Police is yet to decide whether the incident was an accident or a case of negligence, he added.