The blaze broke out around 8:45 p.m. in the 300 block of North Front Street.
Chopper 6 video showed heavy flames engulfing the structure, which sustained significant damage. Portions of the roof and interior floors have collapsed.
As of 11 p.m., crews were still working to bring the fire under control.
Crews battle massive fire in Allentown Pa.
Authorities urged residents on the 300 block of North Front Street to evacuate through the rear of their homes. Residents in surrounding areas were advised to shelter in place until further notice
No injuries have been reported.
Officials said those displaced can seek shelter at Resurrected Life Church at 620 W. Hamilton Street.
Several road closures remain in effect as emergency crews continue to work in the area.
Thousands of PPL customers were without power Wednesday night due to the fire.
The cause of the blaze remains under investigation.