TIL

What is Rocky Flats?
Rocky Flats is located between Golden, Colorado and Boulder, Colorado. In 1951 the US government started a major nuclear weapons factory center there. Its purpose was to process plutonium into metal and to make plutonium bomb cores. Rocky Flats was one of the Denver area's largest employers.

Why was it raided and by whom?
On June 6th, 1989, a team of FBI agents dressed in plain clothes walked into the Rocky Flats nuclear weapons facility. They said they needed to inform the facility officials about a threat from an eco-terrorist organization. In reality, the agents were there to buy time while 30 vehicles with more than 70 armed agents made their way to the plant. As soon as they were ready, the FBI agents told the facility officials why they were really there. The FBI believed the plant was illegally burning hazardous waste. It was the first time in U.S. history that one government agency had raided another.

Throughout its operation, there were reports of the plant violating environmental regulations. Thousands of leaking barrels contaminated the soil and nearby water reservoirs with toxic waste. Two major fires occurred at Rocky Flats, one in 1957 and another in 1969. Both fires released dangerous amounts of radioactive waste into the air. The public was never notified about the 1957 fire. The event only came to light when scientists at the University of Colorado recorded that the contamination near the plant was the highest ever recorded near a city—including Nagasaki after the bombing. The 1969 fire was barely even mentioned in the news despite it being the most expensive industrial accident in U.S. history at the time.

TL;DR
U.S. nuclear trigger manufacturing plant buried thousands of pounds of radioactive waste, had multiple fires releasing radiation, very lax safety and workplace rules.
Got raided by federal agents.

Radioactive Sauce: https://outrider.org/nuclear-weapons/articles/rocky-flats-raid#:~:text=Thousands%20of%20leaking%20barrels%20contaminated,notified%20about%20the%201957%20fire.