The deceased were believed to be contract workers, he said.
Three injured people have been admitted to a private hospital here, he said, adding that the condition of one of them, who suffered 40 per cent burns, is stated to be critical.
The blast reportedly occurred in a water tank on the front side of the ship docked in the yard for repair.
The incident occurred at around 10 AM when those on the vessel were about to deboard it for breakfast break.
Police said smoke inhalation is suspected to be the reason for the casualties.
"Shocked by unfortunate blast at Cochin Shipyard... My heartfelt condolences to bereaved families. I have spoken to MD, Cochin Shipyard n asked him to provide all necessary medical support to victims n to initiate immed inquiry with help of concerned agencies (sic)," he tweeted.
In a Facebook post, he said directions have been issued to conduct rescue operations and provide urgent medical care to those injured in the blast.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)