LAS VEGAS (AP) — The operator of a closed radioactive waste dump that caught fire in southern Nevada had trouble over the years with leaky shipments and oversight so lax that employees took contaminated tools and building materials home, according to state and federal records.

The firm, now called US Ecology Inc., had its license suspended for mishandling shipments in the 1970s — about the same time that state officials say the material that exploded and burned last weekend was accepted and buried.

Nevada now has ownership and oversight of the property, which opened in 1962 near Beatty as the nation’s first federally licensed low-level radioactive waste dump and closed in 1992. State officials said this week they didn’t immediately know what blew up.

A soundless 40-second video turned over by US Ecology to state officials showed bursts of white smoke and dirt flying from several explosions on Oct. 18 from the dump in the brown desert about 110 miles northwest of Las Vegas.

A state fire inspector, Martin Azevedo, surveyed the site on Wednesday.

His report, obtained Friday by The Associated Press, described moisture in the pit and “heavily corroded” 55-gallon drums in and around the 20-foot-by-30-foot crater. Debris from the blast spread 190 feet. Two drums were found outside the fence line.

Jon Bakkedahl, state radiation control supervisor, said previously the material that exploded was probably buried in the mid-1970s.

Federal records say 4.7 million cubic feet of materials was buried before the 40-acre waste site closed. Officials say there are 22 trenches up to 100 feet deep and 800 feet long, with pits capped by up to 10 feet of clay and dirt.

The permit was for low-level solid radioactive waste, including contaminated tools, protective clothing, machine parts, medical items and laboratory supplies.

US Ecology, which was formerly known as Nuclear Engineering Co., said this week the Nevada radiological waste facility operated “under a different name and different ownership,” and referred questions about the fire to state officials. Nuclear Engineering Co. changed its name in 1981 to US Ecology.

The company today has 15 hazardous materials treatment, storage and disposal facilities around the country — including a 40-acre hazardous materials dump accepting toxic polychlorinated biphenyls, or PCBs, adjacent to the closed Beatty radioactive disposal site.

“We offer a service that is required for businesses to comply with complex state and federal regulatory requirements that were established to ensure waste is managed safely and properly,” company spokesman Dave Crumrine said in email replies to questions.

Nevada state emergency management chief Caleb Cage said operating records for the damaged trench, No. 14, were in Department of Health and Human Services archives and weren’t immediately available.

The scramble to find the paperwork illustrates problems posed by lax regulation and oversight in the years before and immediately after the federal Environmental Protection Agency was established in 1972. The Beatty dump is not an EPA superfund cleanup site.

“Regulations and waste management practices have evolved since the 1960s and 70s,” a US Ecology statement noted.

Former Nevada Gov. Robert List ordered the Beatty low-level waste facility shut down in 1979 and launched a probe after a radioactive cargo fire on a truck parked on U.S. Highway 95 at the facility gate.

The fire came three years after employees were dismissed for pilfering radioactive building materials, tools and even a portable cement mixer, according to a 1994 report prepared by the Idaho National Engineering Laboratory.

Operations at Beatty resumed “only after assurance was given by the federal government that the rules governing shipments … would be enforced,” according to the Idaho lab report.

List expressed doubt that anyone will ever know what’s really underground at the site. “Good luck with that,” he said. “What we found when we did our investigation was they had very, very skimpy records about what was there.”

Former U.S. Sen. Richard Bryan, a Democrat who was governor from 1983 to 1989, remembers “an ongoing series of problems” at the Beatty site, including several episodes involving leaking trucks.

The radioactive dump covers half an 80-acre property turned over to the state in 1997 and now administered by Health and Human Services. It is an island amid federal land. Nevada leases a surrounding 400-acre buffer from the federal Bureau of Land Management.

US Ecology was fined nearly $500,000 by the U.S. Environmental Protection Agency in 2010 at its hazardous industrial waste recycling and disposal plant after inspectors found leaky containers and operating logs showing smoke emissions containing hazardous wastes had been improperly vented in 2008. Inspectors also found poor record-keeping.

“US Ecology fully cooperated with the EPA, remediated all areas of concern, and the matter was closed,” Crumrine said. “We are confident there was no impact to human health or the environment.”

Crumrine said the facility was fined one other time since 2005, paying $6,200 after the state found an open container.

Bryan recalled hearings about what was being sent to the site when he was state attorney general and List was governor.

“At no time was there any statement made by the company or by any federal official that what was buried at Beatty had a potential to catch fire,” Bryan remembered.