At least 20 persons were killed and several others injured in an powerful explosion in a firecracker factory in Balaghat district of Madhya Pradesh on Wednesday, police said. "An explosion in the firecracker factory in Katera village in Kotwali police station jurisdiction around 3.30 p.m. was so powerful that even factory walls collapsed due to the impact," said Additional Director General of Police G. Janardan. Earlier, According to Janardan, 18 bodies have been recovered from the blast site and relief and rescue operation is underway. "More bodies could be lying under the debris," the ADGP added. The seriously injured have been rushed to hospital. A couple of people are still feared to be trapped under the debris, said District Collector Bharat Yadav. The cracker factory is owned by one Warish Ahmed. According to Yadav, the victims were the workers of the factory and the incident took place when the work was on. "What exactly triggered the fire is not yet known. It is possible that someone might have thrown a burning beedi," he said. The fire has been doused, he said adding the factory was located away from the human settlement.