Federal prosecutors charged Wednesday that the Chicago branch of a Colombian heroin trafficking organization operated inside the city water department, already awash in allegations that trucking companies received department business in exchange for payoffs.

Eight individuals were arrested Wednesday morning in Chicago and one in New York on charges involving an alleged conspiracy to distribute sizable quantities of heroin on the city streets.

Among those charged was Gerald A. Prado, a hoisting engineer for the city's water department and the leader of the distribution cell, according to federal prosecutors.

Also charged were Prado's brother-in-law, Anthony C. Ritacco, and Michael D. Hart, both identified by federal officials as low-level employees in the city water department.