ULAN BATOR, May 15 (Xinhua) -- A Mongolian court on Tuesday extended the detention of a former finance minister held in custody for alledged abuse of power in a large mining deal after prosecutors demanded more time to investigate the case.

Ulan Bator's Chingeltei District Court extended Sangajav Bayartsogt's custody by an additional month once his current detention period expires on Wednesday.

Bayartsogt signed an agreement on behalf of Mongolia with Canada's Ivanhoe Mines in 2009 to develop Oyu Tolgoi copper-gold mine, granting a 66-percent controlling stake to the company.

Ivanhoe Mines subsequently changed its name to Turquoise Hill Resources and is now majority owned by Australian-British mining giant Rio Tinto.

The Independent Agency Against Corruption, Mongolia's top anti-corruption body alleged that Bayartsogt used his influence and position to provide the other parties to the agreement an advantage in negotiations.

Mongolia's two former prime ministers, Sanjaa Bayar and Chimed Saikhanbileg, are also in custody over corruption allegations in the mining deal.

Mongolian government signed the original 2009 investment agreement during Bayar's term, as well as the financing arrangement of the deal was revised in 2015 during Saikhanbileg's term.

The Oyu Tolgoi copper-gold mine, located in the South Gobi Desert of Mongolia, 80 km north of Mongolia's border with China, is expected to produce an average of 430,000 tons of copper and 425,000 ounces (about 12,050 kg) of gold annually for 20 years.