The explosion occurred in a ballast tank of the ONGC drill ship 'Sagar Bhushan', which was at Cochin Shipyard for about two months.
Even though the shipyard has an effective control mechanism, and despite the presence of firemen on the ship, many people were injured and five killed because the explosion took place inside a tank, local media informed.
Workers at the ship suffered burn injuries and were transported to a hospital, with the condition being reported as critical.
Firefighting operations and rescue services are deployed to minimize the fire and conduct rescue operations. Moreover, medical care is provided to the victims and other officials are on the site to help, India's Ministry of Shipping said.
The cause of the incident is still uncertain, according to ONGC.