(CNN) -- A special team of federal inspectors are looking into an incident at an Ohio nuclear power plant in which higher-than-normal radiation levels were detected in a work area, the U.S. Nuclear Regulatory Commission said Tuesday.
According to an NRC statement, the company that runs the plant in Perry, Ohio, 35 miles northeast of Cleveland, said the incident was not believed to have exposed workers to unsafe radiation levels.
Viktoria Mitlyng, an NRC spokeswoman, said five workers were involved in the incident, some of them plant employees and others contract workers. She was unable to provide the exact radiation levels detected.
The incident involved the removal of a "source range monitor" from the reactor core on April 22, the NRC statement said, adding that the plant was shut down for refueling at the time. Source range monitors measure nuclear reactions during "start up, low power operations and shutdown conditions," the statement said.
"While performing the activities to remove the monitor, workers at the plant identified an increase in radiation levels in their work area," the NRC statement said. "The workers stopped and immediately left the area when the higher than expected levels were identified. The licensee does not believe the workers received radiation in excess of NRC limits."
The statement said the Perry Nuclear Power Plant was "in a safe condition, and there has been no impact to workers at the plant or members of the public from this issue."
A special inspection team arrived at the plant Monday to determine what happened and evaluate any potential radiation exposure, according to the NRC statement.
Mitlyng said she didn't know how long the inspection would last.
Last week, FirstEnergy Nuclear Operating Company announced that the Perry Nuclear Power Plant shut down for scheduled refueling and maintenance.
The maintenance involved replacing 284 of the 748 fuel assemblies, a company statement said, with "numerous" safety inspections taking place while the unit was offline.