At 7:55 PM on January 29, 1986, residents of the mining town of Dalnegorsk in Primorsky Krai in the Soviet Far East observed a bright reddish-orange sphere approximately three metres in diameter flying silently over the town. The object made several jumps in altitude, lost control, and crashed into the rocky flank of Izvestkovaya Mountain (locally 'Hill 611') at an elevation of approximately 611 metres. The impact site was observed continuously burning for more than an hour — an unusual phenomenon given the rocky terrain and winter conditions. Within two days, Soviet military, Academy of Sciences, and KGB Far Eastern Directorate investigators had cordoned off the impact area.
The Dalnegorsk investigation, led by astrophysicist Valeri Dvuzhilni of the Far Eastern Branch of the Soviet Academy of Sciences, collected an unusually rich set of physical evidence. The soil at the impact site had been fused into black glass-like masses to a depth of several centimetres. Small spherical metallic particles of a size and alloy unknown to Soviet metallurgical science were recovered from the fused zone. Crystalline 'mesh' structures — delicate filaments of gold, silver, and nickel in a composition not found naturally — were identified. A 300% elevation in ambient radioactivity was measured at the site. The recovered material was forwarded to Soviet Academy of Sciences laboratories in Moscow, Leningrad, and Vladivostok; fragments were later shared with Japanese and American researchers after the end of the Cold War.
The Dalnegorsk case is universally regarded as the most physically-evidenced UFO-crash incident of the twentieth century. Subsequent analysis of the recovered alloys, reported in the 1991 journal Tekhnika-Molodyozhi and in Vladimir Azhazha's 1992 monograph 'UFOs Over the USSR,' concluded that the mesh structure 'could not have been produced by terrestrial technology of the period.' Subsequent reports from Dalnegorsk between 1987 and 1989 described additional low-altitude objects, including a repeat of the January 1986 event observed by the same witnesses. The Dalnegorsk case remains central to Russian UFO research and has been formally acknowledged in Russian Ministry of Defense documents released after 1991.