The fertiliser plant that exploded four days ago, obliterating part of a small Texas town and killing at least 14 people, had last year been storing 1,350 times the amount of ammonium nitrate that would normally need to be reported to the US Department of Homeland Security (DHS).
Yet a person familiar with DHS operations said the company that owns the plant, West Fertilizer, did not tell the department about the potentially explosive fertiliser as it is required to do, leaving one of the principal regulators of ammonium nitrate unaware of potential danger. This claim has not been formally confirmed.
Fertiliser plants and depots must report to the DHS when they hold 400lb or more of the substance. Filings this year with the Texas Department of State Health Services, which weren't shared with DHS, show the plant had 270 tons of it on hand last year.
A US congressman and several safety experts have now called into question whether incomplete disclosure or regulatory gridlock may have contributed to the disaster. "It seems this manufacturer was wilfully off the grid," Bennie Thompson, a senior member of the House Committee on Homeland Security, said. "This facility was known to have chemicals well above the threshold amount to be regulated under the Chemical Facility Anti-Terrorism Standards Act (CFATS), yet we understand that DHS did not even know the plant existed until it blew up."
Company officials did not return calls seeking comment on its handling of chemicals and reporting practices. Late on Friday, the plant's owner, Donald Adair, released a statement expressing sorrow over the incident, but saying West Fertilizer would have little further comment while it co-operated with investigators. "This tragedy will continue to hurt deeply for generations to come," Mr Adair said.
Failure to report significant volumes of hazardous chemicals at a site can lead the DHS to fine or shut down fertiliser operations. Though the DHS has the authority to carry out spot inspections at facilities, it has a small budget for that activity and only a "small number" of field auditors, according to someone familiar with the agency's monitoring regime.
Firms are responsible for reporting their volumes of ammonium nitrate and other volatile chemicals to the DHS, which then helps to measure plant risks and devise security plans based on them. Since the agency never received a so-called top-screen report from West Fertilizer, the facility was not regulated or monitored by the DHS under its CFAT standards, which are largely designed to prevent sabotage of sites and to keep chemicals from falling into criminal hands.
The DHS focuses "specifically on enhancing security to reduce the risk of terrorism at certain high-risk chemical facilities", said a spokesman, Peter Boogaard. "The West Fertilizer Co facility in West, Texas is not currently regulated under the CFATS programme."
The West Fertilizer facility was subject to other safety programmes, spread across at least seven state and federal agencies, a patchwork of regulation that critics say makes it difficult to ensure thorough oversight. An expert in chemical safety standards said the two major federal government programmes that are supposed to ensure chemical safety in industry – led by the Environmental Protection Agency (EPA) and Occupational Safety and Health Administration (OSHA) – do not regulate the handling or storage of ammonium nitrate. That task falls largely to the DHS and the local and state agencies that oversee emergency planning and response. More than 4,000 sites nationwide are subject to the DHS programme.
"This shows the enforcement routine has to be more robust, on local, state and federal levels," said Sam Mannan, a director of the process safety centre at Texas A&M University. "If information is not shared with agencies, which appears to have happened here, then the regulations won't work."
Chemical safety experts and local officials suspect last week's blast was caused when ammonium nitrate was set ablaze. Authorities suspect the disaster was an industrial accident, but haven't ruled out other possibilities. The fertiliser is considered safe when stored properly, but can explode at high temperatures and when it reacts with other substances. "I strongly believe that if the proper safeguards were in place, as they are at thousands of CFATS-regulated plants across the country, the loss of life and destruction could have been far less extensive," said Mr Thompson. A blaze was reported shortly before a massive explosion levelled dozens of homes and blew out an apartment building.
A small lorry packed with ammonium nitrate mixed with fuel oil exploded to raze the Oklahoma federal building in 1995. Another liquid gas fertiliser kept on the West Fertilizer site, anhydrous ammonia, is subject to DHS reporting and can explode under extreme heat. Wednesday's blast heightens concerns that regulations governing ammonium nitrate and other chemicals – present in at least 6,000 depots and plants in farming states across the country – are insufficient. The facilities serve farmers in rural areas that typically lack stringent land zoning controls, with many of the facilities near residential areas.
Apart from the DHS, the West Fertilizer site was subject to a hotchpotch of regulation. But the material is exempt from some US chemicals safety programmes. For instance, the EPA's Risk Management Program (RMP) requires firms to submit plans describing their handling of certain hazardous chemicals. Ammonium nitrate is not among the substances that must be reported.
In its RMP filings, West Fertilizer reported its anhydrous ammonia storage and said it did not expect a fire or explosion to affect the facility. And it had not installed safeguards such as blast walls around the plant.
A separate EPA programme, known as Tier II, requires reporting of ammonium nitrate and other hazardous chemicals stored above certain quantities. Tier II reports are submitted to local fire departments and emergency planning and response groups to help them plan for and respond to chemical disasters. In Texas, the reports are collected by the Department of State Health Services. Over the past seven years, according to reports West Fertilizer filed, 2012 was the only time the company stored ammonium nitrate at the facility. It reported having 270 tons on site.
"That's just a God-awful amount of ammonium nitrate," said Bryan Haywood, the owner of a hazardous chemical consulting firm in Milford, Ohio. "If they were doing that, I would hope they would have got outside help."
Mr Haywood, who has been a safety engineer for 17 years, reviewed West Fertilizer's Tier II sheets from the past six years. He said he found several items that should have triggered the attention of local emergency planning authorities – most notably the sudden appearance of a large amount of ammonium nitrate in 2012. "That would have been a red flag for me," he said.
Additional reporting by Ryan McNeill and Janet Roberts