Seven persons were killed and 33 others injured,23 of them seriously,in a fire that broke out at a fireworks unit in Tamil Nadus Virudhunagar district today,officials said. Over 200 people were working in the factory at Namaskarichanpatti near Sivakasi when the fire broke out in a shed where sky display items were being made,they said. As many as 40 sheds were damaged in the fire that soon spread to other sheds and exploded bundles of crackers there. Fire department personnel reached the spot and extinguished the blaze,they said,adding District Collector Sijithomas Vaidhyan also rushed to the spot. Officials said the toll could increase as most of the injured persons were in a very serious condition with more than 60 per cent burns. This is the second such incident in two weeks in South Tamil Nadu. On July 7,19 persons were killed in an explosion in a fireworks factory near Vadakkampatti village in Madurai district.