A pair of postal vans were destroyed and a portion of a postal annex in Lincolnwood, north of Chicago, was burned in a late Monday night fire.
Firefighters were called to the distribution center on the 6500 block of North Lincoln Avenue at about 11 p.m.
Just charred shells of two vehicles remained after crews put out the raging fire that spread into the building through a window.
A fire department spokesman told NBC Chicago that no mail was damaged.
The cause of the fire remained under investigation Tuesday morning.