A fire in an electrical switch room on Tuesday briefly knocked out cooling for a pool holding spent nuclear fuel at the Fort Calhoun nuclear plant outside Omaha, Neb., plant officials said.

The safety of deep pools used to store used radioactive fuel at nuclear plants has been an issue since the accident at Japan's Fukushima nuclear plant in March. If the cooling water a pool is lost, the used nuclear fuel could catch fire and release radiation.

As ProPublica reported earlier, fire safety is a continuing concern at the country's 104 commercial reactors, as is the volume of spent fuel piling up at plants.

Officials at Fort Calhoun said the situation at their plant came nowhere near to Fukushima's. They said it would have taken 88 hours for the heat produced by the fuel to boil away the cooling water.

Workers restored cooling in about 90 minutes, and plant officials said the temperature in the pool only increased by two degrees.

The fire, reported at 9:30 a.m., led to the loss of electrical power for the system that circulates cooling water through the spent fuel pool, according to a report from the Nuclear Regulatory Commission. A chemical fire suppression system discharged, and the plant's fire brigade cleared smoke from the room and reported that the fire was out at 10:20 a.m., the NRC said.

Mike Jones, a spokesman for the plant's owner, the Omaha Public Power District, said Fort Calhoun has a backup pump to provide water to the spent fuel in case the main system is lost. That pump, which runs on a separate power supply from the rest of the plant, was inspected and standing by on Tuesday, but plant operators restored main power to the pool before the emergency pump was needed, he said.

Fort Calhoun's single reactor has been shut down since April for refueling. The plant had already been operating under a heightened level of alert because of nearby flooding on the Missouri River, the NRC said. The cause of the fire remained under investigation this morning.