Two people were killed Friday night, including a child, when a three-alarm blaze raced through an apartment building in Allentown.
Dozens of displaced residents were being aided by the American Red Cross at a nearby elementary school, officials said.
Residents of the Allentown apartment building said the only alarms they heard Friday night were other residents.
"There was pounding on the doors. Everybody was running around through the building frantic. Everybody was screaming," said displaced resident Amy Gross. "They came knocking on my door. I opened my door, and there was thick, black smoke."
The fire broke out just after 11 p.m. Friday, and investigators said it started on the top floor.
"The way the building's designed -- with the hallways and elevator shafts and stuff -- made the fire very difficult to fight, because of the openings," said Deputy Fire Chief Robert Scheirer. "The fire spread quickly from the third floor up into the roof area, as a result of the elevator shafts."
An inter-connected fire alarm system was installed in the building last year, investigators told NBC 10's Byron Scott at the scene. But it was residents who called in to 911 dispatchers, prompting the emergency response.
"No alarms at all went off. Nothing. If it wasn't for each other helping each other out, knocking on doors, there might have been more casualties," Gross said. "... We're just tired, waiting for some answers and waiting to see if we can go back in and get some belongings, what is left. We don't know what's going on."
Fire officials said they were still investigating what caused the fire and whether the alarm system malfunctioned.