Today an extraordinary resource, “Russia’s Necropolis of Terror and the Gulag“, compiled by Petersburg Memorial’s Research & Information Centre (and released in 2016), has been launched in an English version. What follows is an excerpt from that website’s account of Sandarmokh.
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[…] Historians believe that a considerable proportion of those executed in Karelia were shot at Sandarmokh. A transport of 1,111 prisoners from the Solovki Special Prison were brought from the White Sea to the clearing and shot there between 27 October and 4 November 1937.

Many years spent searching for this “lost transport” led to the discovery of the killing field at Sandarmokh on 1 July 1997 by an expedition of the Petersburg and Petrozavodsk Memorial societies led by Irina Flige, Veniamin Joffe (1938-2002) and Yury DMITRIEV. With the support of the district administration, they found 150 grave pits, measuring 4×4 metres, two of which were opened in the presence of a representative of the Medvezhegorsk district prosecutor’s office. Indirect estimates indicate that up to 4,500 bodies were buried in these pits – many more than those of the lost transport from Solovki.
After further investigation, and an assessment by the prosecutor’s office, the Memorial society proposed that a memorial cemetery be created on the site, and this suggestion was supported by the Karelian government and the Medvezhegorsk district administration. […]