Karachi, Sep 12 : Four people were killed and seven others injured when a three-storey residential building caught fire in Pakistan's Karachi city on Saturday, rescue teams said. The fire broke out in the first floor of the building in a densely populated area of the city due to a short circuit, Salman Qureshi, a rescue worker with the Karachi-based NGO Saylani Welfare Trust, told Xinhua news agency. He said that the fire erupted in the early hours of Saturday morning, but rescue work got a bit delayed because of congested roads. Four families were residing in the building. The victims were members of the family who lived on the first floor which was the worst-hit, Qureshi said, adding that residents of the other floors were safely evacuated by the rescue workers. The injured people were shifted to a nearby hospital where one of them who jumped from the third floor in panic, is in critical condition, the rescue worker said. /IANS