Mehmet Bakar, the head of Istanbul's health department, said: "There are 17 dead ... Forty injured people were hospitalised and three of them are in serious condition."
The blast at a five-storey building in the Davutpasa area, on Istanbul's European shore, was believed to be have been accidental.
Muammer Guler, the governor of Istanbul, ruled out the possibility of a terrorist attack.
However, Guler said the cause of the explosion was not known and that the building housed several companies, including a denim bleacher, paint and yarn manufacturers and an allegedly unlicenced fireworks workshop.
According to a medical worker at the scene, the explosion occured in the furnace room of a textile company.