CHICAGO (CBS) — Chicago’s Inspector General says some city contractors and subcontractors are underpaying their workers, and that violates the law.

The Inspector General’s Office said its audit shows that a number of prime contractors and subcontractors for City Services are not paying the salaries required under Chicago’s Base Wage Ordinance. WBBM’s Political Editor Craig Dellimore reports.

IG Joe Ferguson reports, for example, that four prime contractors for security and janitorial services were paying proper wages, but three of the four subcontractors were under-paying their workers by as much as about $3 an hour.

The IG is recommending that city officials make the contractors pay any back wages owed, and put in better controls to monitor compliance with the law.