An icy road in Russia’s Siberian region of Irkutsk has been covered with sand mixed with human bones.

Photos posted on social media over the weekend showed fragments of bones and skulls on the surface of the road in the town of Kirensk 5,400 kilometers east of Moscow.

It’s thought they could belong to victims of the Russian Civil War, in which an alliance of anti-communist forces tried to topple Vladimir Lenin’s Bolshevik dictatorship from 1917 until the early 1920s.

Russians commenting on social media drew parallels with the Kolyma Highway in Russia’s far East, which is often called the Road of Bones due to the estimated 250,000 – 1,000,000 people who died while constructing it.

The workers were forced labourers in the Gulag prison system during the Stalin era and many were buried underneath or beside the road.