The incident took place when the samples were being tested (Representational)
At least 11 people including nine women were killed and two others injured in explosions at two firecracker units in Tamil Nadu's Virudhunagar district on Tuesday.
The accidents at fireworks units took place in Rangapalayam and Kichanayakanpatti villages.
The police said the units had a valid licence and that an investigation was underway.
Police said that seven charred bodies were recovered from the sudden blast at the fireworks unit in Rangapalayam, and their identities are yet to be established.
In Kichanayakanpatti, the explosion killed a man and injured two women workers, who have been admitted to the Srivilliputtur Government Hospital for treatment.
Tamil Nadu Chief Minister MK Stalin condoled the deaths and announced a compensation of Rs 3 lakh for the families of the victims.
Earlier on October 9, ten people were killed in an explosion at a fireworks unit in Tamil Nadu's Ariyalur district.
Ahead of Diwali, the production of firecrackers has increased at factories in Tamil Nadu.