Srinagar: Four paramilitary troopers and three policemen were injured on Monday in an explosion in Pulwama district of Jammu and Kashmir, police said. The explosion occurred in Pulwama town inside a vehicle in which four troopers of the Central Reserve Police Force (CRPF) and three local policemen were travelling, the police said. While initial reports said the explosion had been caused by a grenade hurled at the vehicle by separatist guerrillas, top police officials now say that a tear smoke shell exploded accidentally inside the vehicle. The injured have been taken to hospital for treatment. Meanwhile, a gunfight started on Monday between a group of heavily armed guerrillas and the security forces in the Rajwar forests of Kupwara district of the state.