Weeks after a French nuclear watchdog reported unusually high levels of specific nuclear isotopes in the atmosphere over Europe, the Russian meteorological service released a statement that seems to support their findings.

Earlier this month, the French Radioprotection and Nuclear Safety Institute (IRSN) released reports of unusually high levels of ruthenium-106 in the air over Europe.  That isotope is not naturally occurring, and can only be created by splitting atoms inside a nuclear reactor.  That specific isotope has a particularly short half-life, and is not believed to be present any health risks to the European populous, though IRSN reported that wherever the leak originated would undoubtedly have faced an emergency of significant proportion at the time of the leak.  According to their models, the breach must have occurred near the end of September.

Russia denied knowledge of any radioactive breach upon the report’s release, though IRSN believes the source of the leak must have been somewhere between the Ural Mountains in the north and the Volga River in the south, meaning the source of the radiation must be in either Russia or northern Kazakhstan.

A new report released by Roshydromet, Russia’s state owned weather service, corroborated those findings to an extent, per a statement released on Tuesday.  According to Roshydromet, Russian researchers found “extremely high pollution” of ruthenium 106 in samples collected in two different research stations in the Southern Ural Mountains.  One of the samples was collected in late September and the other in early October.

At the Agrayash weather station measured levels of ruthenium-106 increased by nearly a thousand times as compared to samples collected a month previously.  That particular weather station is only about 20 miles away from Mayak, a reprocessing plant for nuclear fuel that produces material for medical research and industrial applications.  The plant has denied that there has been any leak at the facility, however, and Russia has denied knowledge of a leak if there has been one.

The northern and southern boundaries of where the leak was believed to have occured, with the Mayak nuclear facility marked in the middle.

The Novogorny weather station, which is significantly further away from Mayak, reported a level increase of only 440 times.

Because ruthenium-106 has been found in elevated levels but other nuclear isotopes are absent, scientists believe the leak must not have been the result of a reactor breach or nuclear detonation, but must have been a leak at a plant similar to Mayak.

The increased levels of just one isotope “suggests a leak from a fuel/reprocessing plant or somewhere they are separating the ruthenium,” according to Professor Paddy Regan at the University of Surrey.