Asian Football Confederation president Bin Hammam quickly denied any wrongdoing just days before the June 1 election in which he is challenging Sepp Blatter, the Swiss standing for a fourth term as head of football's world governing body.
CONCACAF president Jack Warner was also placed under investigation following the insider report which, to add to the intrigue, was made by his own general secretary Chuck Blazer.
Bin Hammam, Warner and Blazer are all members of FIFA's powerful executive committee and the latter pair have held their respective positions with CONCACAF for 21 years.
FIFA said Qatar's Bin Hammam and Trinidad & Tobago's Warner will face an ethics committee hearing in Zurich on Sunday, three days before the governing body's presidential election, along with two officials from the Caribbean Football Union (CFU).
Blazer - a striking figure with a bushy grey beard - made his report followed a meeting of the CFU on May 10/11 which was attended by Warner and Bin Hammam and which FIFA said was linked to the presidential campaign.
"This has been a difficult and painful day for me today," Bin Hammam said in a statement.
"This move is little more than a tactic being used by those who have no confidence in their own ability to emerge successfully from the FIFA presidential election.
"Here I completely deny any allegations of wrongdoing either intentionally or unknowingly while I was in the Caribbean.
"I am confident that there is no charge to answer and that I will be free to stand in the FIFA presidential election on June 1 as originally planned."
The meeting referred to by FIFA was organised so Bin Hammam could state his election case to delegates. He had been unable to attend the CONCACAF Congress in Miami on May 3 after being denied a visa for the United States.
Bin Hammam has used the campaign to call for reform at FIFA, which has been mired in claims of corruption surrounding last year's vote to choose hosts for the 2018 and 2022 World Cups.
FIFA POWERBROKER
Warner, seen as a FIFA powerbroker but also one of its most controversial members, told Britain's Daily Telegraph newspaper that he was not aware of any wrongdoing on his part.
FIFA's statement read: "Chuck Blazer reported to FIFA secretary general Jerome Valcke possible violations of the FIFA code of ethics allegedly committed by officials."
"In view of the facts alleged in this report, which include bribery allegations, Jerome Valcke requested the FIFA Ethics Committee to open ethics proceedings."
CONCACAF, the North and Central America and Caribbean Confederation, holds 35 of the 208 votes at the FIFA Congress which will choose the president.
Warner has always been regarded as a staunch Blatter supporter but said his confederation had not yet chosen who it would back this time.
The 68-year-old has been in trouble before.
In December 2006, FIFA expressed disapproval with him over a scandal involving the resale of World Cup tickets by son Daryan through Warner's former travel company.
No further action was taken after FIFA's disciplinary committee said there was "no concrete evidence" Warner had known about the sales.
Warner was also criticised by national team players in his native Trinidad and Tobago over his involvement in negotiating the bonuses awarded to members of the 2006 World Cup squad.
In 2008, football officials from Dominica threatened to take Warner to FIFA's ethics committee after he visited the tiny Caribbean island and recommended the removal of the Dominica Football Association's (DFA's) executive committee.
The DFA said Warner had m
