NEW DELHI, March 23 (Xinhua) -- At least five people were killed and 15 others injured in an explosion inside fireworks factory in India's eastern state of Bihar, officials said Friday.

The blast took place inside the factory on Thursday night in Bihar Sharif of Nalanda district about 79 km south of Patna, the capital of Bihar.

"Late last night in Khasganj Mohllah, a blast took place inside a fireworks factory, killing five and injuring 15 others," a police official said. "The injured were immediately removed to nearest medical facility and among them seven critical persons have been referred to the Patna Medical College hospital."

Local media reports said the factory was operating illegally. The explosion also damaged four nearby buildings, locals said.

The district administration has ordered an inquiry into the incident.