Kerala Chief Minister Oommen Chandy and Home minister Ramesh Chennithala are expected to reach the spot soon.
The injured have been rushed to Trivandrum Medical College and Kollam General Hospital.
Police have confirmed the death toll to local media. Local TV channels blamed the accident on firecrackers used in temple celebrations, according to Indian Express.
It has been reported that one of the firecrackers sparked a cache of pyrotechnics, which caused a massive explosion, the Times of India says.
Multiple victims have been admitted to hospitals in Meeyapuram and Kottiyam areas with burns, while those severely injured are being treated at the government medical college. Overall, more than 200 people suffered from burns.
The tragedy occurred just a few days before the Vishu festival in Kerala on April 14, which marks the Indian New Year and is celebrated on various dates across the country.
The celebration, widely known as the festival of light and fireworks, traditionally sees an abundance of pyrotechnics displays. Police, however, say the temple had been warned against setting of fireworks before, and the site had no permit to do so.