(Recasts with police investigation of leaked emails)
By Mfuneko Toyana and TJ Strydom
JOHANNESBURG, June 5 (Reuters) - South Africa's elite police unit opened an inquiry on Monday after thousands of emails relating to alleged fraud in awarding government contracts were leaked, adding to a graft scandal that has deepened splits in the ruling African National Congress.
Last week, AmaBhungane, a non-profit group that has a strong track record of exposing what it says is government corruption, released some of more than 100,000 leaked emails and documents.
"An inquiry has been opened ... obviously, we will look at the authenticity of these emails, how were they leaked, but this is something that we've just started," a spokeman for the Hawks police unit, Hangwani Mulaudzi, said.
AmaBhungane said last week the emails show companies owned by the Gupta family unduly influence the awarding of government contracts worth hundreds of millions of dollars. Reuters was not independently able to verify the allegations.
Zuma has denied wrongdoing and the Gupta family and its companies have also denied all allegations of influence-peddling or improper dealings.
Gary Naidoo, a spokesman for the Gupta family, did not respond to calls from Reuters for comment on Monday.
Factions in the ANC are battling for control before a party conference in December where they must choose a successor to President Jacob Zuma. He has survived two no-confidence votes in the last six months and can stay in power until a 2019 election.
The 75-year-old has survived political and personal scandals before, fending off accusations of graft and rape before he took office in 2009. Parliament is expected to hold a no-confidence vote on Zuma this year. He has survived those before too.
Allegations against the Gupta family were investigated last year by the Public Protector, an anti-graft watchdog, whose report in November called for an judicial inquiry but did not say any crimes had been committed.
Separately on Monday, River Group said it had ended its role as corporate governance adviser to Oakbay Resources, majority owned by the Guptas, citing "association risk".
Other businesses that have severed links with Oakbay include auditors KPMG, investment bank Sasfin and all four major banks: Standard Bank, Barclays Africa, Nedbank and FirstRand.
"The reason for River Group's termination of their services is due to their revised assessment of association risk surrounding the company and its shareholders," Oakbay said in a regulatory filing, without giving further details.
That gives Oakbay 30 days from July 31 to find a new sponsor, required under Johannesburg Stock Exchange rules, otherwise its listing could be suspended.
Principal partner at River Group, Andrew Lianos, told Reuters his firm had a history of not being involved in politics and wanted to maintain this track record.
"We feel that politics has no place in business-related matters and in view of the ongoing developments over the last six months we had no option but to review our position," he said. (Editing by Tiisetso Motsoeneng and Louise Ireland)