The pair were detained Wednesday as authorities investigate their handling of two agreements related to the massive Oyu Tolgoi gold-copper mine, which has been mired in controversy for years.
At the request of the nation’s anti-corruption agency, two courts on Thursday ordered that both be held for 30 days in a detention centre.
Sanjaagiin Bayar, prime minister from 2007 to 2009, resigned for health reasons weeks after Mongolia signed an agreement with Canada’s Ivanhoe Mines and Rio Tinto to develop the mine near the Chinese border.
The court ordered his arrest after a warrant was issued over fears that he might destroy evidence – claims that his lawyer rejected, saying that the documents related to the deal were kept in government archives.
Chimediin Saikhanbileg, who served between 2014 and 2016, was detained after returning to Mongolia from the United States to cooperate with the investigation.
He wrote an open letter saying he “didn’t violate the law” or take bribes in a 2015 deal with Rio Tinto for multi-billion-dollar expansion of the mine.
“I’m not afraid or ashamed,” he wrote.
A former finance minister and a former chief executive of Erdenes Oyu Tolgoi, the Mongolian state-owned company that controls a third of the mine, have been arrested in connection with the investigation.