Samuel Moreno, mayor of Bogotá, and his predecessor Luis Eduardo Garzón are under investigation by Sandra Morelli, Colombia’s Controller General, for corruption in the awarding of contracts for Bogotá’s TransMilenio public transit system. Ms. Morelli moved Tuesday to freeze the financial assets of both the incumbent and ex-mayor.

The TransMilenio dilemma began when Mr. Garzón paid Grupo Nule, a Colombian contracting firm, approximately $36 million in late 2007 to construct a route from downtown Bogotá to El Dorado International Airport, which serves the Colombian capital. Grupo Nule did not adhere to mandated specifications for the project’s insurance policy and subsequently went bankrupt in 2010 during Mr. Moreno’s administration, leaving the Colombian taxpayers with the roughly $104 million bill.

Mr. Garzón is being investigated in part because Grupo Nule was paid only three days before the end of his mayoral term, which has raised suspicion. The Controller General’s investigation includes Moreno for what it quotes as “passive behavior” in not proactively monitoring irregularities that arose during the TransMilenio project that was mostly engineered during his term.

Mr. Moreno has professed his innocence and has thus far rebuffed calls to step down from office.