In February of 2014, 22 people were exposed to radiation, a radiological waste repository was indefinitely shuttered, and $240 million in damage was sustained when a drum exploded at a nuclear waste dump. The accident’s culprit? The wrong kind of kitty litter.

It has taken investigators a year and a 277-page report to officially call it – the February 2014 radiation leak accident at New Mexico’s Waste Isolation Pilot Plant near Carlsbad was caused by the wrong brand of kitty litter, NPR reported.

In case you’re wondering what kitty litter and nuclear waste dumps have to do with each other, here’s a brief lesson: Cat lovers know that the material is very absorbent, making it perfect for absorbing nuclear waste. For years, kitty litter has been used in “cleanup activities” at nuclear facilities, NPR added.

However, there was one critical problem with the kitty litter sent to the Carlsbad dump. It was switched from inorganic clay litter to organic litter, NPR reported. When the kitty litter was mixed into a drum of waste, it “sparked a chemical reaction causing it to heat up and generate gases that dislodged its lid, spewing radioactive materials,” Reuters explained.

The report suggests more than just kitty litter was involved, however; a variety of “chemically incompatible” contents, of which the litter was just one, is apparently to blame. The explosion, which was confined to a single drum and took place a half-mile below ground, caused a leak that churned out radioactive uranium, plutonium, and americium throughout the facility.

Right after the accident, the U.S. Energy Department believed the exploding drum was improperly packaged at the Los Alamos National Laboratory long before it got there for disposal. Regardless, the facility – which is the government’s only place to permanently store radiological waste associated with nuclear labs and weapons sites – has been shut down since the kitty litter accident. It could be another two years before it opens up again.

Unsurprisingly, the Waste Isolation Pilot Plant has been criticized since the accident for its slack attention to safety. Luckily, the 22 people exposed to radiation after the kitty litter explosion are not expected to suffer long-term health problems as a result.

[Photo Courtesy Getty Images/Christopher Furlong]