At least 100 people have died following an explosion at the Hindu temple in the Indian state of Kerala.
The explosion and blaze are believed to have been sparked by fireworks.
The fireworks, which were to be used to celebrate a local new year festival, exploded about 03:30 (10.15pm GMT Saturday).
A building at the temple then collapsed, causing many of the deaths. More than 200 people were injured.
Indian Prime Minister Narendra Modi, who has flown to Kerala, said the incident was "heart-rending and shocking beyond words".
The fireworks had been stored ready for celebrations of Vishu, a Keralan festival marking the Hindu new year.
The local district magistrate had denied permission for the display to be held this year because of safety concerns and complaints from residents.
The Kerala government has ordered an investigation, and the police are planning to take action against the temple administration and the contractors who were putting on the display.
"There was no permission to even store the fireworks," Kerala's Chief Minister Oommen Chandy said.
The explosion happened as the Duke and Duchess of Cambridge arrived in Mumbai for a seven-day tour of India and Bhutan.
They had been informed about it and sent their thoughts to all who were assisting the victims, Kensington Palace said.