Washington state's only commercial nuclear power plant stopped operations Friday after an automatic shutdown system failed to work properly.

State emergency officials said there was no release of radiation and no danger to the public.

The reactor, which is operated by Energy Northwest (search, will remain out of service until crews determine what caused the problem, said Brad Peck, spokesman for the company.

The automatic shutdown system was triggered by an indication of high pressure, said Ken Clark, a spokesman for the Nuclear Regulatory Commission (search). As part of the shutdown, all 185 control rods were supposed to insert into the reactor. But lights on a control panel indicated that two rods failed to insert, said Heather McMurdo, a spokeswoman for Energy Northwest.

Backup systems operated correctly after the rods, which control the reactor's operation, were inserted manually, she said. Operators kept the plant shut down as a precaution, McMurdo said.

The reactor is located on land leased from the U.S. Department of Energy (search) within the boundaries of the Hanford nuclear reservation in south-central Washington state, but is a separate entity.