Two more Chicago water department employees have pleaded guilty in the city’s Hired Truck scandal, adding to the already lengthy list of individuals involved with the corrupt program.

Roger McMahon, former director of administration and finance for the Chicago Water Department, and Charles M. Romano, a former operating engineer with the department, each pleaded guilty to one count of mail fraud on Wednesday, May 18, the Chicago Tribune reported.

McMahon told prosecutors he collected payoff cash and campaign contributions from outsourced trucking companies in exchange for city work through the city program, The Associated Press reported. According to media reports, the program cost Chicago taxpayers $38 million.

McMahon also admitted to delivering the payoff money to former first deputy water commissioner Donald Tomczak, who was second in command in the water department at the time. Tomczak pleaded innocent to charges in a separate investigation, the Tribune reported.

So far, nine individuals have been convicted or pleaded guilty to charges in the scandal, and investigators told the Tribune they are expecting that list to grow as more people are indicted for their involvement.