The explosion occurred in a front tank of the ONGC vessel Sagar Bhushan at 9.15 am. It could have been due to "gas consolidation (inside the tank)",CSL chairman and Managing Director Madhu S Nair said, citing immediate reason for the blast.
He, however, said that the exact reasons would be known only after adetailed investigation.
Firefighters were called in and 12persons were immediately evacuated from the ship following the blast and admitted to various hospitals.
In a statement, the CSL said that five people died and seven were injured in the fire incident.
The condition of one person who suffered 45 per cent burns was serious. Others are out of danger, Nair said.
The CSL said that "at around 0915 today, a phone call was received at CSL informing that there is a gas leakage near the AC compartment area of the ship MODU Sagar Bhushan, undergoing repair in the drydock No 1".
"Immediate instruction was passed on to stop all the hot works. By this time explosion had occurred in the forward area of ship, near to the AC plant. Immediately a fire tender rushed to the ship along with ambulance," it said.
Fire men onboard the ship immediately started firefighting and the fire tender joined them for the fire fighting from the Aft area, it said.
The deceased were identified as CSL senior fireman Unnikrishnan C S, short term contract employee safety assistant Gevin,contract fire watchman K B Jayan and two employees of a contract firmRamshad M M and Kannan MV, Nair said.
CSL has announced an immediate ex gratia of Rs 10 lakh for the kin of the deceased. All treatment expenses of the injured will be met by the company as per the existing policies, the company said.
"Besides this, all statutory obligations will be followed to support the victims families," Nair told reporters here.
He said CSL has begun a high level internal inquiry into the incident.
Detailed technical investigations will be carried out by DG Shipping and Factories and Boilers Department.
City Police Commissioner M P Dinesh visited the accident site and said those trapped on the ship were evacuated and the situation was under control now.
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.
CSL said the vessel had arrived at Cochin Shipyard on December 7, 2017 for drydock repairs.
It was drydocked on January 12, 2018 and it was to be undocked on Feb 28, 2018. The work completion was scheduled by April 7, 2018.
"CSL places health, safety and environment (HSE) as one of its core value in operations," the company said.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)