At least five people were injured in an explosion inside a shop in Kamarhati area near Calcutta on Tuesday afternoon, police said.

The police are yet to ascertain the cause of the blast.

However, an officer said it could be a gas cylinder explosion or a bomb blast.

"The injured five people are undergoing treatment in a hospital. Of them, the condition of two seems to be critical,” he said.

The incident took place at around 12.15 pm inside the shop in North 24 Parganas district, where cooking gas cylinders were allegedly refilled illegally.