"I saw a lot of black smoke - there was smoke pouring out of the windows.''
She said the police were already at the scene and were doing a great job at directing traffic.
Those heading south were being told to do a U-turn.
Wilson said she saw two men standing outside the building who were visibly upset.
"They were pretty distressed and upset watching the fire.''
GT SOUTH RD, DRURY - ROAD CLOSED - 7:20AM Due to a large fire emergency services have CLOSED a section of Great South Rd in Drury - between Parkhaven Dr & Sutton Rd. Diversions are in place. Avoid this route or allow extra time this morning. ^TP pic.twitter.com/VrRjQQaa2l