California Sen. Barbara Boxer is pressing federal regulators to open a probe into equipment problems at the shuttered San Onofre nuclear power plant.
Her letter Wednesday to the Nuclear Regulatory Commission comes as Southern California Edison is pushing a plan to restart one of the reactors.
A statement says the Democrat wants the NRC to investigate what she calls new information that shows Edison and the company that built the plant's ailing steam generators were aware of design problems before the equipment was installed.
The statement says it raises concerns the company rejected safety modifications and sidestepped a more rigorous safety review.
Southern California Edison said in a statement that its leadership "takes very seriously all allegations raised by the letter."
"The plant has provided voluminous records, data, information and other accurate reports as requested in the months since the plant was safely shut down," the statement says. "SCE will continue its own internal work and we respect the NRC's inspection process. SCE is strongly committed to the transparent review of its operations at San Onofre and the safety of the public and its employees.”
The NRC said in a statement it will respond to the letter "in the normal course of business."
In an interview with KPBS on Wednesday, San Diego Mayor Bob Filner said the NRC must hold a public hearing requiring proof from Edison the plant is safe to restart.
San Onofre has been shut down for more than a year after unusual damage was found in tubes that carry radioactive water.