The mishap occurred at Plot Number 70 where the labourers were breaking a Russian vessel Giovana. The police said that while breaking apart the ship, the labourers struck a gas tank containing carbon dioxide gas. The gas leak caused asphyxiation and five labourers died on the spot before they could even escape. All the labourers were in the age group of 18 to 25 years.

Five of the six labourers belonged to the Koli community and hailed from Mathavda village of Talaja taluka. The deceased have been identified as Vinod Popat, 25, Vikram Shiyal, 24, Abal Koli, 20, Ashok Koli, 18, Bharat Solanki, 25, and Karim Shaifu Sheikh.

According to Bhavnagar District Collector Raj Kumar, preliminary investigations revealed that there appeared to be negligence on the part of the Mukadam or labour contractor -Karim Sheikh - who left the chamber containing carbon dioxide gas open which spread into other compartments where the labourers were working. Sheikh himself died at the Bhavnagar Civil Hospital.

``The government has ordered a magisterial inquiry into the accident,'' Kumar told The Indian Express. After visiting the mishap site in the afternoon, he informed that post-mortem reports revealed that the labourers had inhaled the deadly carbon dioxide and were asphyxiated even before they could come out of the compartments.

Explosive experts from Ahmedabad are likely to visit the site on Wednesday to investigate further.

The ship-breaking yard plot is owned by R K Industries. The owner Mukesh Patel is also the president of the ship breakers' Bhavnagar Industrial Gas Manufacturers Association (BIGMA). The Bhavnagar Ship Breakers Association has, so far, not reacted to the incident.