Firefighters scrambled Wednesday to contain a blaze at a US nuclear waste plant in New Mexico, while underground staff were evacuated and some taken to hospital, officials said.

The blaze erupted on an underground vehicle carrying salt at the Waste Isolation Pilot Plant (WIPP) near Carlsbad, New Mexico, the US Department of Energy (DoE) said in a statement.

"Emergency response teams are responding to an operational emergency" at the plant, which is used to dispose of radioactive waste left from making nuclear weapons.

"All underground personnel are accounted for and have been safely evacuated to the surface," it said, adding: "There is no waste in the vicinity of the fire."

All waste handling operations have been suspended while "multiple employees" were transported to a local hospital for potential smoke inhalation after the blaze, which erupted around 11:00 am, it said.

The site is "the nation's first repository for the permanent disposal of defense-generated transuranic radioactive waste left from research and production of nuclear weapons," according to the DoE.

Further details were to be released at a media briefing.