Indian Prime Minister Narendra Modi is travelling to the scene.
Narendra Modi tweeted that the accident was “heart-rending and shocking beyond words”.
Those with most serious burns injuries are being treated at the government medical college in Thiruvananthapuram, the state capital.A building at the temple then collapsed, causing many of the fatalities. More than 200 are injured.
The impact of the blast was felt in houses up to a kilometre away.
“Huge pieces of concrete were flying through the air. Chunks landed in our yard,” said resident Jayashree Harikrishnan.