The arrested were four persons who had taken the Omshakthi fireworks factory complex, where the fire broke out, on lease and its foreman, police said.
Three more persons succumbed to burn injuries today, taking the the toll to 39, District Revenue Officer R Raju said. The condition of over 40 of the 70 people injured was stated to be serious in various hospitals.
The licence of the factory was suspended only two days ago prior to the accident and the entire products had been stored in a godown against rules, according to officials.
The fire that broke out when workers were mixing chemicals to make fancy fire crackers was so intense that the factory and 48 sheds in the complex exploded in flames, trapping many in the raging inferno.
A factory official said 300 persons were at work at the unit at the time of the mishap.
Cracker units at Sivakasi, accounting for 90 per cent of firecracker production in the country, function at `breakneck speed` ahead of the Deepavali festival.