At least 40 people were killed, more than half of them children, when a fire tore through dozens of homes in a shanty town in Pakistan's largest city Karachi, officials said Friday. Initial reports indicated the blaze in the teeming southern port city was sparked by a power wire that fell onto the roofs of the huts, said the health minister of Sindh province, Saghir Ahmed. City police official Majid Dasti said that investigators were also looking into the possibility that residents had started a small fire to beat the cold, and that the wind whipped the flames out of control. Twenty-two children were killed in the blaze, which broke out just before midnight (1900 GMT Thursday) when most residents were asleep, city police Waseem Ahmad said. Two people died in hospital in the hours after the fire, taking the toll to 40, Ahmad said. More than 20 people were injured, some of them suffering severe burns, said Mashhood Zafar, an official at the Abbasi Shaheed Hospital in Karachi. An AFP photographer at the scene said more than 30 huts had been gutted in the massive blaze. The provincial health minister said the huts destroyed had been home to about 200 people. The shanty town was surrounded on three sides by larger buildings, and the only escape route appeared to have been quickly blocked by the flames, firefighters said. "Most of the casualties seem to have been caused by the lack of exit route," said fire brigade official Ehtesham Salaam. It took firefighters several hours to bring the inferno under control. "Investigations are ongoing," said Dasti, adding that police did not suspect foul play.