More than 70 firefighters attended the blaze off Craddock Street and Gatis Street. After getting on top of the blaze and extinguishing it, an investigation unit has since been looking into the cause.
Residents described 'shocking' scenes and told of how they could feel the heat from the fire in their living rooms.
Shasta and Zainab were in a house directly behind the warehouse while it was ablaze and had to evacuate in the middle of the night.
Zainab said: ""We started hearing crackles at sharp noises so we ran downstairs and all we could see was complete fire, it was mental.
"One of the neighbours was running around banging everyone's doors telling everyone to leve their houses."We could feel the heat in the front room, the fire officers said it was good that we evacuated because we would have been told to anyway.
"They told us it was safe to go back at around 2.30am, the kids haven't been to school because we were up so late.
"It was a nightmare, we were told if we hadn't moved our cars the windows could've smashed from the heat."
Police and paramedics were also sent to the scene but nobody is thought to have been hurt.
The steel-framed warehouse includes offices and belonged to the Grasshopper baby clothing company before becoming an Xercise4Less gym in 2014.