Four men, including two brothers, were killed and three injured in a mysterious blast at Shireen Jinnah Colony on Tuesday. The oil tanker, which arrived in the city from Saindak, Balochistan, carrying scrap metal two days ago, was being repaired for a fault in its gearbox. A mechanic was using a piece of scrap metal as a hammer when the blast occurred. Seven people, including the owner of the oil tanker Alam Zaib, his younger brothers Abdul Haq and Ziaul Haq, tanker driver Mohammad Rehman and cleaner Salman were seriously injured. They were taken to Ziauddin Hospital where doctors declared four of them dead on arrival. Ziaul Haq is said to be in critical condition. Police, Rangers and bomb disposal squad (BDS) officials scanned the site for traces of explosive material. BDS officials said the explosion was probably the result of unexploded ordnance, possibly a piece of a landmine, that was among the scrap metal brought by the tanker.