Thousands of people had gathered at the temple precincts to witness the fireworks display which were on since midnight.
The mishap occurred as sparks fell on the storeroom 'Kambapura' and exploded with a thundering noise at around 3.30 AM, police said.
The sound of the explosion could be heard over a km radius.
The whole area plunged into darkness as the power supply went off and people ran helter skelter, eyewitnesses said.
More From This Section
"Rescue operation at the mishap spot is over...The next main focus of the government is to provide best treatment to the injured," he told PTI.
Asked about the death toll, the Chief Minister said the number would go up as reports are pouring in from different hospitals, where the injured have been admitted.
"This is an unprecedented and alarming situation," Chandy said.
The government would extend treatment facilities to the injured persons in the hospitals preferred by their relatives, he said.
Home Minister Ramesh Chennithala told PTI that 63 people were confirmed dead and over 150 are said to be injured.
Officials fear the toll could go up.
According to police officials, over 200 were injured in the mishap.
Many bodies have been charred and a DNA test would be conducted to ascertain the identity of the deceased.
Health Minister V Sivakumar said the district collector
"We are giving all support to the injured persons. 83 injured people have been admitted to the Trivandrum Medical College," he said.
The state home minister said the situation was under control and the DGP is on the spot and coordinating rescue operations.
"Now the fire is under control. Fire and police personnel are coordinating the rescue operations," he said.
"Kerala government is going to initiate a judicial inquiry in the whole affair," he said.