Valley Metro says light rail service was suspended along Washington Street between 28th and 34th streets Tuesday afternoon and passengers were being bussed to other locations.
There's no word yet on how the two-alarm fire started, but investigators are on the scene.
Phoenix firefighters were called to the area for a fire near 29th Street and Washington Street about 1:45 p.m.
It appears the exterior fire extended to a large warehouse that houses Paramount Promotions, a digital printing company that also does vehicle wraps.
The fire sent large clouds of black smoke billowing over the downtown area.
Copyright 2015 The Associated Press modified.