Over 100 North Korean laborers were involved in the construction of a stadium for one of Russia’s largest football clubs, which will also be used in the 2018 World Cup, according to a Norwegian investigative report published on Tuesday.

The article, published by Josimar Football magazine, includes interviews with laborers of other nationalities who had observed North Koreans working longer hours than others on the site, while under intense surveillance and controls.

“Josimar can reveal that at least 110 North Koreans have worked at the Zenit Arena in St Petersburg, one of the venues for the 2018 World Cup Finals,” an introduction