Four persons were injured on Monday in an explosion inside a Border Roads Organisation (BRO) camp near Sonamarg hill station in Ganderbal district of Jammu and Kashmir.A senior police officer told IANS here, "Four persons were injured an explosion inside a BRO camp near Sonamarg in Ganderbal district today.""The exact cause of the explosion is being ascertained, but it is mostly likely an accidental explosion as the BRO uses explosive material for road-laying operations in the mountainous areas," he said.The injured have been taken to hospital, the officer said.