A fire at the Parkland View Apartments is not considered to be suspicious, according to Upper Macungie Township fire commissioner Grant Grim.
Flames tore through 14 apartments at the complex along Cetronia Road on Sunday morning resulting in extensive damage.
Firefighters were back at the scene on Monday, checking for hot spots.
Grim said the windy conditions only made matters worse for firefighters.
Several volunteer fire departments from the county were dispatched to the blaze on Sunday morning.
"The sprinklers did work. Everything was working properly," said Grim. "The fire got into the roof in the attic space where it was not sprinklered."
On Twitter, the American Red Cross of Lehigh Valley and Bucks County reported it was assisting 20 adults and three children displaced from the blaze.
The cause of the fire remains under investigation by the Pennsylvania State Police fire marshal.
No injuries were reported.