At least four people were killed and 18 others were injured in a powerful explosion here in Sri Sathyasai district of Andhra Pradesh on Wednesday, a police official said. Though the explosion, which demolished at least two houses, was being attributed to a gas cylinder blast, it may not be limited to a gas cylinder, given the intensity of the blast, the official said. "Until now, four people died, and 18 others were injured, including one in a serious condition," the official told reporters. Earlier, Sri Sathyasai district superintendent of police S Satish said the explosion occurred around 12.30 pm. He said workers from Telangana were living in that house where the explosion occurred.