A gas leak has killed three workers who were constructing the Shin Kori 3 nuclear plant in the south-eastern city of Ulsan, South Korea. The victims fell unconscious and later died in hospital. Â
The state-run Korea Hydro and Nuclear Power Company has yet to confirm the cause of death but a nitrogen leak from an underground cable is suspected. Nitrogen is used during construction at nuclear plants to control pressure and to slow the oxidation of equipment.  Â
The South Korean labour ministry has launched an enquiry into the accident. Yoo Han-bong, head of the Labour Ministry in Ulsan, said: "We will promptly conduct an investigation and hold accountable those who are responsible if any irregularities are discovered."Â
Power plants in South Korea were at high alert after hackers gained access to operation manuals for the nuclear reactors. There was no indication that this was related to the fatal accident.Â
The plant is expected to be completed in June 2015.
