World Bulletin/News Desk

Two under construction nuclear reactors were shut down Saturday in South Korea following the deaths of three workers who apparently inhaled toxic gas from a leak.

The state-run Korea Hydro and Nuclear Power Co. announced earlier that nitrogen gas leaking from an underground cable may have caused the deaths Friday at the construction site of a nuclear reactor in Ulsan city, about 410 kilometers southeast of capital Seoul.

The Labor Ministry said Saturday it will launch an investigation into the site with the cooperation of the emergency management agency, the occupational safety agency and police, according to South Korea’s national news agency.

"We will promptly conduct an investigation and hold accountable those who are responsible if any irregularities are discovered," Yonhap quoted Yoo Han-bong, head of the ministry's Ulsan branch, as saying.

The New Gori No. 3 reactor, which was 99 percent complete and scheduled to launch full operation in June, had been undergoing a test run since last month. Meanwhile, the New Gori No. 4 reactor was 98 percent complete.

The nearby Gori and Wolsong nuclear power plants have been the subject of much scrutiny in recent days, after an anonymous Twitter user began to leak information about their facilities -- threatening to unleash chaos if certain reactors were not shut down by Christmas.

Energy Minister Yoon Sang-jik spent the night at Gori on Christmas Eve and told residents of the government’s plans to ensure their security.

Despite Seoul’s repeated calls for calm, an official investigation this week pointed to the possibility that a clandestine team of North Korean hackers in China may have been behind the release of documents.

The United States reached a similar conclusion over the recent cyber attack on Sony Pictures, which almost led to the abandonment of its now highly-publicized movie, “The Interview”.

But Friday’s apparently unrelated gas leak in Ulsan was also a reminder of the physical safety concerns South Korea has faced this year -- most notably after April’s Sewol ferry disaster, which claimed more than 300 lives.