This article was reproduced with the kind permission
of the British Broadcasting Corporation
7 November 2007, 09:59 GMT
A man in a cloak and skeleton mask lit the Annihilation 500 in California Wines on Tonge Moor Road in Bolton.
Greater Manchester Police said their inquiry is focusing on the Tonge Moor area and they want the retailer who sold the firework to come forward.
Insp Tony Kenyon said: "We are lucky we are not dealing with a tragedy."
Shopkeeper Hoam Dimh kicked the large firework into the porch after it was thrown into his shop last Monday.
The firework then went off, firing about 500 rockets in a small, confined space.
He suffered minor burns to his hands and his young son, who was in the flat above the shop, was taken to Royal Bolton Hospital as a precaution after vomiting due to smoke inhalation.
The firework was 42cm (16.6in) in diameter, 10cm (4in) high and weighed 1.2kg (3lbs).
Police said that manufacturers' advice states people should stand at least 25ft (7.6m) away from it when lit.
The offender was seen running into the side streets at the back of the shop after the attack.
Insp Kenyon said: "This powerful firework could have had devastating consequences and we are lucky that we are not dealing with a tragedy.
"I am grateful for the public's help so far in trying to solve this case but I am sure that there is further information within the community.
"A small baby had to be taken to hospital as a result of this irresponsible act and it is a miracle that no one was more seriously hurt."