According to an FIR lodged, the incident took place on July 20 when the two sisters, aged 16 and 18, boarded a Wazirabad-bound van from Sambrial city.
As the other passengers disembarked on different stops, the driver parked the van at a deserted place near Farid Town and tied the girls in the van. Later, five of his accomplices joined the driver and conductor and gangraped the girls at gun-point, police said.
Efforts are on to arrest the driver Yasir Razzaq, conductor Bilal and their accomplices.