In 1989, a small capsule containing highly radioactive caesium-137 was found inside the concrete wall of an apartment building, with a surface gamma radiation exposure dose rate of 1800 R/year.
The source, originally a part of a radiation level gauge, was lost in the Karansky quarry. The gravel from the quarry was used in construction. The cesium capsule ended up in the concrete panel of Apartment 85 of Building 7 on Gvardeytsev Kantemirovtsev Street, between apartments 85 and 52.
Over 9 years, two families lived in Apartment 85. A child's bed was located directly next to the wall containing the capsule. By the time the capsule was discovered, 4 residents of the building had died from leukemia and 17 more had received varying doses of radiation. The accident was detected only after the residents requested that the level of radiation be measured in the apartment by a health physicist. Part of the wall was removed and sent to the Institute for Nuclear Research (NASU), where the cesium capsule was removed and disposed of.
The total number of deaths is alternately reported as 2, 4 (3 children and one adult), or 6 (4 children and 2 adults).