Mongolian authorities released the country's former finance minister, Bayartsogt Sangajav, and the former CEO of state-owned investment company Erdenes Mongol, Byambasaikhan Bayanjargal, Reuters reported June 13.

The country's anti-corruption agency arrested them in April as part of an investigation related to the Oyu Tolgoi copper-gold project in Mongolia, owned by Rio Tinto unit Turquoise Hill Resources Ltd.

Authorities were probing a frozen bank account tied to Sangajav that Swiss court documents indicated was used to pay him US$10 million in 2008.

The investigation is centered on suspected abuse of power related to a 2009 agreement to develop Oyu Tolgoi and a 2015 financing agreement for expanding the mine between Rio Tinto, Turquoise Hill and the Mongolian government.

Sangajav and Bayanjargal have been barred from leaving the country. Mongolia's Independent Authority Against Corruption also detained two former prime ministers in April, Bayar Sanj and Chimed Saikhanbileg, who were serving in 2009 and 2015, respectively.