However, they said that federal agents are looking into financial ties between Gamble, retired UAW Vice President Jimmy Settles -- who now works for Detroit Mayor Mike Duggan -- and a vendor named Jason Gordon, who supplied UAW trinkets to the union, such as T-shirts and key chains.
Specifically, the sources said, the FBI is looking into whether that vendor gave cash kickbacks or bribes to UAW leaders in exchange for their help in securing trinket contracts. They are also looking into a tip that some of those bribes were handed over at the Bouzouki strip lounge in Greektown, possibly by a middleman, the sources said.
But Gamble himself is not a target, they said.
Gamble has adamantly denied any wrongdoing, pledging transparency and accountability for the UAW since he took over presidential duties of the union last year.
"I want to say this clearly to all UAW members and staff: I would not have accepted the role of president if I couldn't withstand the scrutiny that I knew this job would bring," Gamble wrote in a letter to union staff on Thursday in a response to allegations first reported in The Detroit News.
Gamble acknowledged working with Gordon's business, Custom Promotions, in its role as a union vendor, but defended the relationship.
"In all those years of working with this vendor, they never approached me in any manner that was less than professional or questionable in any way, and I absolutely never requested or received any cash or kickback from that vendor or any other. Nor did I ever approach them in any unprofessional or questionable manner," Gamble states in the letter.
Moreover, Gamble said that when he became vice president of the union's Ford Department, which predated his role as president, he instituted a "strict three-bid process for all purchases over $5,000" and that any successful bids were the result of winning that competitive process.
Gamble also said he never solicited money from any vendor for his GIVES charity, which, in line with new union policies, is no longer operating, and he said all proceeds went to help homeless people and provide lunches for underprivileged children.
"I will continue to be transparent and very direct about any issues that come up concerning me personally or this union. Our union has suffered enough as a result of corrupt leaders," Gamble wrote. "My sole focus as president is to strengthen the union's financial controls, oversight and accounting system -- and most importantly, to restore the trust of our union members."