The toll in the mishap at the decommissioned submarine INS Vagli docked at the port here rose to two on Tuesday as another person succumbed to anoxia, police said.

Bhavani Shankar (47), owner of the contracting firm who tried to rescue his employee, Mahendran (36) from a manhole-like structure inside INS Vagli succumbed to the adverse impact in absence of oxygen, police said.

Mahendran (36), who had gone inside the submarine on Monday, fainted in absence of oxygen and later died.

Two other workers, one belonging to the contracting firm (Jayakumar, 24) and another staffer of a private rescue agency (Karan Singh) who also tried to rescue Mahendran, are being treated at a government hospital.

Chennai Port Trust Chairman Atulya Mishra told PTI that the workers were carrying out work to make “mooring” operational.

“The submarine is under State (Tourism) government’s control. They had employed a contractor to make it fit to tow the vessel to Mamallapuram,” he said.

INS Vagli, belonging to the “Foxtrot class” was among Indian Navy’s oldest submarines when it was decommissioned on December 9, 2010 after 36 years of service.

The vessel was gifted to the Tamil Nadu government by the Navy. It was brought from Visakhapatnam Naval base to Chennai in March 2013.

The submarine is likely to be among the prime attractions at the Tamil Nadu Maritime Heritage Museum proposed to be set up near the Mamallapuram World Heritage temple site by the State government.