TOKYO (AP) _ A nuclear reactor in southwestern Japan automatically shut down Wednesday after monitors detected an irregularity, the plant's operator said.

There was no danger of radioactivity leaking out, said Hirokazu Terashima, a spokesman for Kyushu Electric Power Co. No one in the plant was hurt in the emergency shutdown, he said.

The reactor in the city of Sendai on Japan's main southern island of Kyushu shut down Wednesday morning after monitors detected something unusual about a valve connected to a pipe sending steam to a turbine, Terashima said.

He said plant officials were investigating the cause of the trouble. Sendai is 610 miles southwest of Tokyo.

Resource poor Japan depends on nuclear power for about one-third of its electricity needs.