A massive blaze swept through a fireworks factory in south Indian state of Tamil Nadu on Wednesday, killing at least 33 people and injuring dozens more, some with serious burns, police said.

Most of the dead were workers in the factory in the town of Sivakasi, the centre of India's firecracker industry, about 540 km southwest of Chennai.

Television channels showed huge clouds of smoke billowing out of the factory, with repeated bursts of firecrackers resounding in the background. Rescue teams used makeshift stretchers to ferry victims to ambulances.a

Police were unable to determine how many of the plant's 250 workers remained trapped inside as the fire raged out of control.

'We have not been able to enter the factory because of the smoke. The number of casualties may rise,' the deputy police chief, who identified himself only as Ramamurthy, told Reuters.

The fire broke out in the fully-stocked warehouses and flames and smoke quickly spread through the factory. An explosion took place while chemicals for the firecrackers were being mixed in the morning, police said.-Reuters