An explosion at a gas station in Ghana's capital killed at least 78 people late on Wednesday, many of whom had sought shelter there from torrential rain, a fire brigade spokesman said.The blast was caused by a fire that erupted in a nearby lorry terminal at around 10 p.m. (2200 GMT) then spread to the gas station and other buildings in Accra, Prince Billy Anaglate told JOYFM radio.Initial signs suggested the fire started by accident, he added.Firefighters battled the blaze into the early hours while police and soldiers joined emergency crews helping rescue people trapped in the wreckage, said city Mayor Oko Vanderpuije.Floods from several hours of heavy rains submerged buildings and vehicles across the city on Wednesday.