ZURICH (Agencies) - In a stunning twist just days ahead of FIFAs presidential election, footballs governing body said Wednesday it is investigating challenger Mohamed bin Hammam for bribery in his campaign to unseat Sepp Blatter. FIFA summoned Asian Football Confederation leader bin Hammam and FIFA vice president Jack Warner to an ethics hearing on Sunday to face allegations of corruption in the Qatari officials presidential election bid. The allegationslevelled by Warners longtime ally Chuck Blazer of the United Stateswill likely wreck bin Hammams already fading hopes of defeating Blatter in the June 1 vote by FIFAs 208 national members. In view of the facts alleged in this report, which include bribery allegations, FIFA secretary general Jerome Valcke requested the FIFA ethics committee to open ethics proceedings, the football body said in a statement. The ethics panel can provisionally suspend officials under suspicion while it gathers evidence for a full hearing. It took this path when investigating two of bin Hammams FIFA executive committee colleagues prior to the 2018 and 2022 World Cup votes last December. Bin Hammam, under the terms of a provisional ban, could then be prevented from attending any football meeting and effectively barred as an election candidate. FIFA said the allegations related to bin Hammams meeting with 25 Caribbean football leaders on May 10-11 in Warners native Trinidad to lobby for support. This meeting was linked to the upcoming FIFA presidential election, FIFA said. Blatters campaign adviser, Brian Alexander, said the FIFA president would not comment on the case. Bin Hammam helped organize the hastily arranged meeting after he was unable to attend the annual congress of the Confederation of North, Central America and Caribbean Association Football (CONCACAF) one week earlier in Miami. The Qatari official was denied a visa to enter the U.S., despite travelling on a diplomatic passport. His campaigns administrative oversight left Blatter a clear run to lobby for votes in Miami. Warner has long been a key powerbroker in FIFA politics and his backing was seen as vital to bin Hammams hopes. Blatter has been endorsed by confederation leaders in Africa, Europe, Oceania and South America. Warners 35-member confederation has not yet officially backed either candidate. Bin Hammam and Warner are both scheduled to be in Zurich on Thursday for a meeting of FIFAs finance committee, and to attend FIFAs executive committee meeting chaired by Blatter on Monday. They face lengthy suspensions from all football duties if bribery allegations are proven. Both were re-elected unopposed this year to lead their continental bodies for four more years. Two other Caribbean Football Union officials, Debbie Minguell and Jason Sylvester, are also being investigated by FIFA. The four people under suspicion have been invited to take a position by Friday and report to the ethics panel on Sunday, FIFA said. Corruption in FIFA has been a prominent campaign theme after a series of financial and vote-buying scandals severely damaged its reputation during Blatters 13-year presidency. Bin Hammam appeared to have been damaged by association with corruption more than Blatter during their two months of electioneering. Bin Hammam was a key player in Qatars successful bid to host the 2022 World Cup. Qatar was accused in a British Parliamentary hearing of paying $1.5 million bribes to two African FIFA executive committee members, Issa Hayatou and Jacques Anouma. They deny the claims. On Wednesday, a whistleblower from the Qatar bid had been scheduled to submit evidence to Valcke and FIFA legal director Marco Villiger in Zurich. However, FIFA said the whistleblower decided not to attend the meeting based on legal advice.