Horry County firefighters responded to a fire on the fourth floor of a building in the Myrtle Wood neighborhood around 6:30 p.m.
The fire, at 4883 Lusterleaf Court, extended to the walls of the structure, authorities said.
It is not known if residents on other floors have been displaced and the cause is still under investigation.
Myrtle Beach Fire Rescue provided mutual aid.
A second fire started around 7 p.m. on Rose Moss Road in the Conway area. Horry County crews arrived to smoke showing in the single wide home.
Contact AMANDA KELLEY at 626-0381.