Officials investigating a leak from the US government’s only underground nuclear waste dump tried in vain on Monday night to reassure sceptical New Mexico residents that it posed no health risk.

More than 250 people attended a two-hour meeting to ask questions about recent back-to-back accidents at the Waste Isolation Pilot Plant near Carlsbad and the release of radiation.

An increase in airborne radiation was detected in New Mexico on Monday.

The US Department of Energy said the results were from samples collected last week at nearby air monitoring stations.

Last week, US officials confirmed a leak at the facility, which stores plutonium-contaminated waste from Los Alamos National Laboratory.

Waste shipments to the site were also halted earlier this month after a salt lorry caught fire underground.

“I’m just a mum,” said resident Anna Hovrud, “and my first reaction was to start praying.

“Basically I’m not understanding about two-thirds of what has been said.

“Is there a chance we could be exposed to radiation, that we are being poisoned somehow, while we are waiting for these samples?”

But Department of Energy Carlsbad manager Joe Franco told Ms Hovrud that “there is no risk to you or your children.”

Still, some were not convinced.

“I feel like they are not telling us everything,” said resident Leah Hunt.

And police were brought in after mayoral candidate Martin Mills repeatedly and heatedly heckled officials.

Safety officials said it would be weeks before teams could get underground.