Media playback is unsupported on your device Media caption The BBC's Jane O'Brien takes an underground tour of the nuclear waste site before the radiation leak

Maintenance and safety lapses were at the root of a lorry fire that shut down the only US underground nuclear waste repository in February, a report says.

The report also cited problems with emergency response and oversight at the Waste Isolation Pilot Plant (WIPP), outside Carlsbad, New Mexico.

The state's two senators called the findings "deeply concerning".

WIPP, which holds specific kinds of defence nuclear waste, remains closed after a radiation leak last month.

It is still unclear if the fire and the leak, which contaminated 17 workers, are related. A separate report on the leak is expected in the upcoming weeks.

The accidents are the first major incidents at the salt repository, which began taking radioactive waste from US defence sites 15 years ago.

'Nuclear versus mine'

In a report released on Friday, the US energy department's Accident Investigation Board (AIB) found the 5 February fire was preventable.

The root cause, the board wrote, was the failure of the current and previous contractors running the site to "adequately recognise and mitigate the hazard regarding a fire in the underground".

Lorries carrying salt were not maintained or cleaned often enough to prevent the build-up of combustible materials and the onboard automatic fire suppression system had been deactivated.

Image caption The underground entrance to the lift at WIPP

"A nuclear versus mine culture exists where there are significant differences in the maintenance of waste-handling versus non-waste-handling equipment," the report said.

At a community meeting in Carlsbad on Thursday to preview the report, the lead investigator, Ted Wyka, praised the 86 workers who were half-mile underground in the mine when the fire started, saying they "did everything they could" to tell others to evacuate.

But a number of safety systems and processes failed, Mr Wyka said. Emergency strobe lights were not activated for five minutes and not all workers heard the evacuation announcement.

One worker also switched the air system from normal to filtration mode, which sent smoke billowing through the tunnels.

Six were treated for smoke inhalation after the fire.

Jose Franco, who runs the energy department's field office in Carlsbad, choked up as he addressed the meeting, saying that at first, he took the findings personally.

"But I think what's important [is] we definitely got away with not ... having anyone seriously hurt," Mr Franco said. "So we need to learn from that. It is what I wanted to hear, and I wanted the truth. We don't need any sugar-coating."

Hours before, the current contractor at the site demoted the facility's president and project manager.

While the report cited the site's contractor and the field office for gaps in oversight, it also recommended the agency headquarters needed to "re-evaluate resources" applied to WIPP.

In February, Eddy County Commissioner Susan Crockett told the BBC there had been "a lag in funding for maintenance at WIPP".

"We've been asking for $10m for the last three years just for maintenance," she said.

Testing of the underground site has continued since the leak and workers are expected to re-enter the site as early as this weekend.