Excerpts from the ChicagoTribune.com:

Chicago Fire Department Ambulance 42 was in the 300 block of North Michigan Avenue Thursday evening when a cab hit its back quarter panel about 5:50 pm.

The patient inside was not injured from the crash and the ambulance driver kept going to Northwestern Memorial Hospital as the cab followed it.

The cab was not badly damaged and the cause of the crash was not known.

thanks Dan