Under the impact of the explosion, walls of the old house were severely damaged.
Four people, including a 22-year old man allegedly running an unlicenced crackers outlet, were killed in Kancheepuram on Tuesday when firecrackers and some raw materials exploded accidentally at his premises, police said.
Retailer Mushtaq, and three others, including two women, were killed in the explosion which took place at his residence while he was arranging the firecrackers and raw materials.
Under the impact of the explosion, walls of the old house were severely damaged.
The firecrackers that exploded were "locally made, unbranded and more powerful than the branded ones," a senior official told PTI.
Though the firecrackers and raw materials were procured from those holding explosive licence, the man did not have a licence for retail sale of crackers, he said.
Mushtaq's father Maideen was being questioned, the official said adding a case has been registered and a probe was on.