A nuclear reactor at South Korea's Younggwang Nuclear Power Plant automatically shut down Monday after its reactor protection system gave warning signals, plant operators said.

The Reactor-6 at the Younggwang plant, located some 330 kilometers southwest of Seoul, was shut down at 2:57 p.m., according to an official from the state-run Korea Hydro & Nuclear Power Co., Ltd.

"An investigation is currently underway to confirm what has exactly caused the automatic shutdown of the reactor," the official told Yonhap.

According to the official, a warning signal and automatic shutdown can be caused by a number of reasons, including low pressure of the reactor's cooling pump and a change in the pump's speed. (Yonhap News)