Federal regulators have ordered inspections of all Illinois nuclear power plants after an emergency at one reactor and a series of leaks of radioactive tritium at plants owned by Exelon Corp. of Chicago.

The Nuclear Regulatory Commission ordered the inspections Monday, a few hours after officials at Exelon Nuclear declared an emergency at its LaSalle Generating Station in LaSalle County. The inspection of the LaSalle plant is related to the emergency there, while the other inspections were ordered because of the tritium leaks, said NRC spokesman Jan Strasma.

Company officials said the turbine control system at the LaSalle plant malfunctioned as workers were shutting down a reactor for refueling. At 12:28 a.m., operators declared a "site-area emergency," the second-highest of the four emergency categories in the NRC's emergency response system.

Exelon released a statement Tuesday saying preliminary data suggests all the reactor's 185 control rods were properly positioned into the core within four minutes of the declaration. State and federal safety regulators said there were no releases of radiation.

In Will County, the state's attorney's office began an investigation this month into why Exelon did not disclose until recently a series of radioactive tritium wastewater leaks between 1996 to 2003 at its Braidwood Generating Station, about 60 miles southwest of Chicago.

Then last week, Exelon said it found elevated levels of radioactive tritium in water that leaked from two other plants: the Dresden plant in Grundy County and the Byron plant, about 25 miles southwest of Rockford.

Strasma said Monday that inspections would be done at all Illinois plants that handle tritium, including six Exelon facilities.

Tritium is a radioactive substance commonly found in small concentrations in most surface water, but is more concentrated in water used in nuclear reactors. Studies have shown long-term exposure -- through drinking or bathing -- can lead to cancer and birth defects.