Police in India have detained five people in connection with an explosion and fire at a Hindu temple in Kerala that killed more than 100 people.

The five men who work at the Puttingal temple in Paravur, are being questioned about an unauthorised fireworks display that sparked the massive explosion.

Authorities have already ordered a judicial inquiry into the incident.

Police are also looking for a number of people, who were in charge of running the temple and the festival.

Many of those killed were crushed when a building collapsed. Photo: BBC

Nearly 400 others were injured near the temple when a faulty rocket fell onto a large stockpile of fireworks.

A building at the temple then collapsed, causing many of the deaths.

Thousands had gathered to watch the display as part of a local new year festival.

Officials say the temple had been denied permission on safety grounds, but it had gone ahead under pressure from a large crowd.

"Five workers have been detained for questioning," Kollam police chief P Prakash told AFP news agency.

"These are not formal arrests. Once they are questioned, only then we will know their involvement and take further steps."

Indian Prime Minister Narendra Modi, who visited the scene and spoke with victims in local hospitals, said the incident was "heart-rending and shocking beyond words".

The temple had been denied permission on safety grounds to hold the fireworks display. Photo: BBC

"The incident is so grave that it is very difficult to describe in words," he added. "People who were 200 metres away were also hurt."

There were scenes of chaos as emergency teams were slow in reaching the area and rescue teams used bulldozers to clear the area looking for survivors.

A power outage hit the complex after the first explosion, further complicating rescue efforts.

Many of the dead were charred beyond recognition and would have to be identified by DNA tests, said Kerala police chief TP Senkumar.

Photo: BBC

The temple had been denied permission on safety grounds to hold the fireworks display but it had gone ahead under pressure from the crowd, officials said.

Police are planning to take action against the temple administration and the contractors who were putting on the display.

Kerala's government said it had ordered a judicial inquiry that would work alongside the police's criminal investigation.

The incident happened as the Duke and Duchess of Cambridge arrived in Mumbai for a seven-day tour of India and Bhutan, and Kensington Palace said the couple's thoughts were with those assisting victims.

Kerala is in the middle of an election for a new state assembly, but political parties have called off campaigning as a mark of respect for the victims.