The Yale School of Public Health’s Humanitarian Research Lab released a report detailing alleged collaboration between Belarus and Russia in the systematic deportation of Ukrainian children on Thursday.

The 66-page report, titled “Belarus’ Collaboration with Russia in the Systematic Deportation of Ukraine’s Children,” analyzes open source information to establish key details regarding the removals. It finds that children between 6-17 years of age have been taken from cities across eastern Ukraine, including Donetsk and Kherson, and transported to at least 13 locations in Belarus. More than 85% of identified children were reportedly accommodated at a facility in Minsk owned by Belarusian chemical producer Belaruskali.

The report says the removals constitute a “joint effort” coordinated through the Union State entity of Belarus and Russia. It implicates high-level officials from both countries, as well as agencies such as Russia’s Investigative Committee and security services in Belarus. Furthermore, report expressed deep concerns about the involvement of public figures like Alyaksei Talai and organizations including nationalist motorcycle gangs in “re-education” programs. Such activities have allegedly included military training exposing children to firearms in some instances. The report concludes that more investigation is needed to determine the full scale of alleged violations and the current whereabouts of transferred children.

The allegations come amidst wider international scrutiny of Russia’s actions in Ukraine. In March, the International Criminal Court issued arrest warrants against Russian President Vladimir Putin and others related to allegations of forcible deportations of Ukrainians. Ukraine also charged Russia with committing war crimes over deportation of orphans in July.

Commenting on the situation, Michael Carpenter, the U.S. Ambassador to the Organization for Security and Cooperation in Europe (OSCE), said that Belarus has completely failed to abide by its OSCE commitments and human rights obligations. International observers have called for immediate action to address the systematic deportation of Ukrainian children and hold those responsible accountable for their actions. Belarusian authorities have so far remained silent.