In a little village called Kalachi, tucked away in the northern region of Kazakhstan, over 120 residents have been hit by a strange malady that has doctors and scientists baffled.

Without warning a person will inexplicably fall into a coma-like sleep they often won’t wake from for days. When they do come to, they’re often left with “debilitating symptoms – dizziness, nausea, blinding headaches and memory loss,” Joanna Lillis reports for the Guardian.

The mystery illness was first officially recorded in the spring of 2013 and has affected about a fourth of the village’s population with some experiencing repeat attacks. The two most recent cases emerged in early March, bringing the total number of incidences, according to Lillis, to 152.

Scientists, along with the government of Kazakhstan, have been scrambling to find a cause for the strange ailment. But despite some strong leads, they have yet to nail one down. Two likely culprits are radon and carbon monoxide poisoning. The symptoms of these problems closely resemble those experienced by Kalachi’s residents. Testing showed unusually high levels of both in some village homes, but still, local officials have ruled them out as a cause.

The scientists involved are determined to find an explanation, however. Thanks to a research coordination commission set up by the Kazakhstan prime minister “by the end of last year over 20,000 laboratory and clinical test had been conducted – on the air, soil, water, food, animals, building materials, and on the residents themselves,” writes Lillis.

Many residents and one Russian scientist interviewed by Newsweek think the cause of the illness may not be coming from Kalachi, however, but rather a site just outside the village. That’s where an old Soviet-era uranium mine lies abandoned since the 1990s.

“In my opinion, a gas factor is at work here,” professor Leonid Rikhvanov from the Tomsk Polytechnic University in Russia told Newsweek. “Radon could be operating as a narcotic substance or an anesthetic. Currently, the underground space of the mine is flooded and gases are being squeezed to the surface.”

The theory is as yet unproven, however—and in the meantime, authorities have chosen to take drastic measures against the sleeping sickness by offering to relocate locals to villages outside the perceived danger zone. Over 100 citizens have reportedly embraced the “voluntary relocation” already, which officials hope to be complete by May.

There are many in Kalachi who don’t want to move and who have no plan to effectively abandon their lives, despite warnings from Rikhvanov and others that more cases are likely to present themselves. But, as one resident told Lillis of the worrisome illness, “They say it affects the brain; they say it gives people headaches, but our headache now is where we’re being resettled.”