Eyewitness video from Eliud Balderas shows a raging fire shooting from the windows of the Lone Star Legal Aid offices.
There is no word yet on how the fire began.
A thick cloud of smoke can be seen rising in downtown at the site of the fire.
Balderas said he was in his apartment when he heard the explosion, and began filming with his smartphone.
Stay with ABC13 Eyewitness News for more on this developing story.