An investigation has found that a radiation leak at an underground nuclear waste dump in New Mexico happened because of the wrong kind of cat litter.

On Thursday, the government scientists concluded that the major accident that took place at the Waste Isolation Pilot Plant (WIPP) near Carlsbad last year was caused by 'chemically incompatible' contents, including the wrong kind of kitty litter, used to absorb liquids.

They said that the 'chemically incompatible' contents took part in a reaction inside a barrel of waste causing it to burst open and spew radioactive materials.

According to a US Energy Department Report, the drum of waste, containing radioisotopes like plutonium, was not packaged properly at the Los Alamos National Laboratory near Santa Fe before disposal.

The summary of the report said that the workers put the kitty litter brand "Swheat Scoop" in to Drum 68660.

Due to the improper mixing, the barrel got heat up and generated gas which caused it to rupture and thus led to the release of radioactive materials.

The summary said, "Experiments showed that various combinations of nitrate salt, Swheat Scoopr, nitric acid, and oxalate self-heat at temperatures below 100°C. Computer modeling of thermal runaway was consistent with the observed 70-day birth-to-breach of Drum 68660".

According to the contractor that operates the plant, Nuclear Waste Partnership LLC, the workers were exposed to radiation in amounts that are not expected to threaten their health.

The report has confirmed the agency's preliminary theories for the cause of the costly mishap. It has confirmed that just one barrel of waste from Los Alamos was to be blamed for the mishap.

The incident, took place on February 14, contaminated 21 people with low-level radioactivity.

As per the September estimations of Energy Department officials, the cost of the initial recovery of the dump would be $240 million, and that it would take two years or more before it gets fully operational.