ULAN BATOR, May 10 (Xinhua) -- A Mongolian court on Thursday extended the detention of two former prime ministers held in custody over corruption allegations in a large mining deal after prosecutors demanded more time to investigate the case.

The two former prime ministers are Sanjaa Bayar and Chimed Saikhanbileg. Ulan Bator's Chingeltei District Court extended their custody by an additional month once their current detention period expires on Friday.

The Independent Agency Against Corruption, Mongolia's top anti-corruption body, is investigating a mining deal signed between the government and Anglo-Australian mining giant Rio Tinto in 2009, during Bayar's term. Saikhanbileg was the prime minister when the financing arrangement of the deal was revised in 2015.