WASHINGTON — The Nuclear Regulatory Commission says three U.S. nuclear power plants need increased oversight from federal regulators, although officials stressed that all are operating safely.

NRC Chairman Gregory Jaczko says the three plants — in South Carolina, Kansas and Nebraska — need more intensive review than other plants because of problems with safety systems or unplanned shutdowns.

Jaczko told a House subcommittee Thursday that the plants "are the ones we are most concerned about" among the 65 U.S. nuclear power plants in 31 states.

Jaczko did not identify the plants, but an agency spokesman said they are the H.B. Robinson nuclear plant in South Carolina, Fort Calhoun in Nebraska and Wolf Creek in Kansas.

The South Carolina plant, which is owned by Raleigh-based Progress Energy, was cited recently by a watchdog group for two near accidents last year.