Three construction workers at a nuclear power plant in Ulsan were sent to a hospital after inhaling toxic gas, officials said Friday.

A decontamination team was dispatched to the Shin-Kori nuclear power plant at 6 p.m. following the accident.

The incident came some days after a group of hackers threatened to “destroy reactors” unless the government shut down three nuclear reactors at the Kori and Wolseong nuclear power plants by Christmas Day. They also told residents near the facilities to leave.

The government came under fire after hackers released several batches of confidential data on South Korean nuclear reactors, starting last week. The hackers calling themselves members of an antinuclear power activist group posted personal information on some 10,000 employees of Korea Hydro & Nuclear Power and continued to release more information on Twitter, including four files of reactor-related information and safety analyses. The reactor operator said the information leaked by hackers was not classified, but general material.

The prosecution said Wednesday that a suspect in the hacking attacks on the reactors used multiple IP addresses based in Shenyang, China.

By Jeong Hunny (hj257@heraldcorp.com)