A hacker who obtained blueprints of South Korean nuclear reactors Sunday posted more internal information on the facilities, including the floor maps, on the Internet, threatening further "leaks" unless authorities close down the reactors.

Using an account named "president of anti-nuclear reactor group," the hacker revealed on Twitter the designs and manuals of the Gori-2 and Wolsong-1 nuclear reactors taken from the state-run Korea Hydro and Nuclear Power Co. (KHNP). The information included details on the facilities' air conditioning and cooling systems.

The hacker signed the posting as president of the anti-nuclear group in Hawaii. 

This was the fourth such posting since Dec. 15. The KHNP has been maintaining that the information leaked by the hackers were not related to core technologies and do not undermine the safety and security of the reactors.

The KHNP manages South Korea's 23 nuclear reactors, which supply about 30 percent of the country's electricity needs.

"If I don't see the reactors being closed on Christmas, I have no choice but to go public with all of the data and go ahead with a second round of destruction," the hacker said.

"I can open to the world 100,000 pages of data that have not yet been revealed," the hacker said in the posting. "You say this isn't confidential material. Let's see if you will take responsibility if the information on blueprints, systems and programs are all disclosed to the countries that want them."

The hacker had leaked the personal data of some 10,000 employees of the KHNP on Monday. On Friday, the hacker demanded the shutdown of the Gori-1, Gori-3 and Wolsong-3 nuclear reactors for three months starting on Christmas, warning that "residents near the reactors should stay away for the next few months."

The government team investigating the leakage said the hacker's IP address was tracked to a PC located in a provincial area. Investigators were sent to the unidentified provincial location as well as to the reactor sites, the team said.

The KHNP said the recent leaks would not affect the safety of its reactor management, although it has stepped up its security posture against potential cyberattacks. (Yonhap)