A nuclear reactor at South Korea‘s Gori Nuclear Power Plant stopped operation Tuesday due to what appeared to be a problem in the reactor’s control system, plant operators said, adding there was no risk of radiation leakage.

The Shingori 1 Reactor was shut down at 8:10 a.m. after a warning signal indicated a malfunction in the control rod, which is used to control the rate of fission of nuclear materials, according to the Korea Hydro & Nuclear Power Co.

It is the first time that reactor, located 450 kilometers southeast of Seoul, has been shut down due to a malfunction since it began commercial operation on Feb. 28, 2011.

An investigation is currently underway to verify the exact cause of the problem, officials from the state-run operator of nuclear power plants said. (Yonhap News)