Fire crews were called to an old Giant Food store on Centreville Road near Manassas just before 11 a.m.
The former grocery store filled with smoke prompting the emergency call. Emergency crews are investigating the cause of the smoke, said Prince William Fire and Rescue spokeswoman Kim Hylander.
The vacant store sits at 8810 Centreville Road near the busy intersection of Liberia Avenue just outside Manassas.
