It happened around 8:27 a.m. on the 1600 block of West Avenue in Ocean City.
Initial 911 calls reported two people trapped in the residence.
Video obtained by Action News showed heavy flames consuming the property as one firefighter was rescued from a second-floor deck. The firefighter was not injured.
Officials say a propane tank valve failed, which resulted in a drastic increase in the volume of fire.
All five occupants of the building were later found safe. One of the residents was taken to an area hospital to be evaluated.
The blaze was placed under control around 9:14 a.m.
American Red Cross is assisting those displaced. The cause of the fire remains under investigation.