At least 15 kg heroin was recovered by Border Security Force troopers on Wednesday following an exchange of fire with Pakistani smugglers in Punjab's Ferozepur sector, a BSF officer said.The heroin is worth an estimated Rs 75 crore in the international market.A BSF ambush team had stationed itself in the area following a tip-off from the Narcotics Control Bureau (NCB) in Amritsar."Based on specific information provided by the NCB about smuggling of narcotics through the International Border, a special ambush was laid at night by the Khalra post troopers," a BSF spokesman said."The team observed suspicious movement near the IB around 2.30 a.m. The Pakistani smugglers began throwing some packets over the border security fence."Our troops challenged them but they opened fire. The BSF also opened fire at the smugglers in retaliation and self-defence," he said.The smugglers, however, managed to escape, taking advantage of darkness and the standing wheat crop and undulating terrain.At least 15 packets of contraband heroin were recovered when the BSF later searched the area.Punjab shares a 553-km-long barbed-wire-fenced International Border with Pakistan.