The US Department of Energy (DOE) said on 12 April that a 55-gallon (208-litre) barrel of radioactive waste had ruptured the previous day at site that includes the Idaho National Laboratory. The barrels are from nuclear weapons production at the Rocky Flats Plant near Denver, Colorado and contain a mixture of fluids and solvents that came from nuclear weapons production. Federal officials said they had activated an Emergency Operations Centre and that crews were responding to the incident at a containment structure within the Idaho Cleanup Project’s Radioactive Waste Management Complex. They added that no one was injured and there was no threat to the public. The facility is designed with high-efficiency filters and no contamination has been detected outside. Workers had been retrieving the waste for shipment to a storage facility in New Mexico. Federal officials said it was the first known rupture of a barrel containing radioactive sludge at the Idaho site but that it might not be the last, given the secrecy of record keeping during the Cold War makes it hard for officials to now know the exact contents of similar barrels. The rupture could possibly slow progress in shipping waste out of the state DOE has already paid $3.5m in missed deadline fines.