DETROIT -- Two more people could end up in federal court facing charges by the end of the week in connection with the alleged bribes for the Synagro Technologies contract.

Embattled political consultant Sam Riddle turned down a second plea deal, Local 4 has learned.

Former politician Mary Waters also had a plea deal to consider over the weekend, but she is not talking about it.

The plea deal expired Sunday, which means Riddle or Waters could be charged with conspiracy to commit bribery in connection with the Synagro Technologies Inc., any day now, sources told Local 4.

Watch: Riddle Turns Down Another Plea Deal
Watch: Riddle, State Rep. Deny Plea Deal

Riddle is under FBI investigation in connection with alleged bribes to win approval of the sewage sludge contract awarded to Synagro Technologies Inc. in 2007.

Riddle has repeatedly said he would not do what his former boss, ex-Councilwoman Monica Conyers, and city businessman Rayford Jackson did, which is accept plea deals and admit guilt to conspiracy to commit bribery.

Conyers accepted a plea deal last month and was charged with one count of conspiracy to commit bribery for reportedly accepting at least $6,000 in cash in exchange for her Council vote of the Synagro contract. She faces up to five years in prison.

Charging documents state that on Nov. 20, 2007, Conyers "met an individual sent by Jackson in the parking lot of the Butzel Family Center in Detroit and received an envelope containing cash." It also states that on Dec. 4, 2007, Conyers and her aide, who has been identified as Riddle, also accepted an "envelope containing cash" in a Detroit McDonald's parking lot.

Local 4 has learned that Riddle is angry that the federal government wants to charge him with more than what Conyers was offered in her plea deal a few weeks ago.

The details of Riddle's plea deal have not been made public.

Riddle and his lawyer, David Steingold, have refused to comment on the case on Monday.

Two people who worked for Synagro have already pleaded guilty: Jackson and James Rosendall Jr. Jackson pleaded guilty June 15 to arranging four bribes in 2007.

Rosendall pleaded guilty last year, accused of trying to influence city officials by chartering private planes to take them to Las Vegas and Mackinac Island, donating about $200,000 to campaign entities of a city official and paying $25,000 to an unidentified city official's relative.

Jackson's brother is also being investigated in connection with the bribery.

The FBI is also investigating Riddle in several other bribery cases. Riddle and state Rep. Mary Waters have been linked to Southfield City Councilman William Lattimore, who was charged with one felony count of bribery.

The investigation involves alleged payoffs to help Southfield jewelry store Ziedmans move from a high-rise location to a stand-alone property at 10 Mile and Evergreen roads.

Waters has not talked about her deal, but Local 4 has learned it would have included pleading guilty to one felony charge and in exchange the feds would not require substantial prison time for the former politician.

A lawsuit claiming Conyers and Riddle bribed a strip club owner for approval to open a club in Detroit is also pending.