CARLSBAD, N.M. (AP) — Emergency crews battled a fire Wednesday at the southeastern New Mexico site where the federal government seals away its low-grade nuclear waste, including plutonium-contaminated clothing and tools.

Six people were taken to the hospital for smoke inhalation after a truck hauling salt caught fire at about 11 a.m. Wednesday at the Waste Isolation Pilot Plant near Carlsbad, N.M.

All employees were evacuated and none of the radioactive waste was impacted, plant officials said.

Authorities said Wednesday afternoon that they weren't sure what caused the blaze.

Melissa Suggs, a spokeswoman for the Carlsbad Medical Center, said the six people brought there were all in stable condition.

At an afternoon news conference, officials said the fire occurred on a truck hauling salt in the north mine, the Carlsbad Current-Argus reported. Nuclear waste is stored in the south mine, officials said.

Officials said fire suppression systems were immediately activated, all waste handling operations were suspended, and rescue teams were deployed.

The repository takes plutonium-contaminated waste from Los Alamos National Laboratory and defense projects. The waste is then buried in rooms cut from underground salt beds.

WIPP is the nation's only deep geological nuclear repository, and its license gets renewed by the federal Environmental Protection Agency every five years, said Rod McCullum, the director of used-fuels programs at the Nuclear Energy Institute.

Nevada's Yucca Mountain is another underground site built as a potential repository for used nuclear fuel, but it is not operational, McCullum said.

WIPP receives 17 to 19 shipments of waste each week from sites around the country, including Los Alamos and installations in Idaho, Illinois and South Carolina.

The plant has strong support from local leaders, McCullum said.