12 displaced after massive fire tears through apartment building in Gloucester County, New Jersey

Part of an apartment building in Gloucester County, New Jersey, collapsed early Monday after a massive fire, displacing a dozen residents.

The fire broke out around 12:45 a.m. at Narraticon Apartments on Hemlock Court in Deptford after fire crews were called to reports of a fire on the back porch of one of the units.

When firefighters arrived, the entire back of the building was heavily involved in flames. Fire officials said the flames were an estimated 50 feet high.

Video submitted to CBS News Philadelphia shows the blaze shooting from the side of the apartment as firefighters worked to put it out.

"The fire was in the back of the building," Deptford Fire Chief Richard Thomas said. "And this asphalt you're seeing here would not sustain a fire truck. Probably would've gotten like 100 feet then sunk."

The fire spread through the second and third floors and to both sides of the building, impacting nine units. The second floor eventually collapsed into the first floor before firefighters were able to bring the fire under control.

The collapse forced crews to switch to a fully defensive operation.

"The fire started on the second floor above me. My neighbors were running around, knocking on the doors," Ken Densten, who lives next to the unit where the fire started, said. "And then when I come out my back door to see what was going on, there were flames going up the side of the building. It was scary."

Densten said his unit mostly sustained water damage.

"I don't even know where to go," Densten said. "Seventy years old, never had to deal with anything like this in my life."

"It was crazy. I was more worried about making sure the neighbors got out. Because it was really kind of crazy. It was a lot of really loud popping and just explosions," Melissa Dwornick, another resident, said. "It was kind of surreal. I've never really witnessed a fire in person like that before."

One person was treated after inhaling smoke but refused further medical treatment, fire officials said. The fire was brought under control around 3 a.m.

Twelve people have been displaced by the fire, according to the American Red Cross. The Red Cross said it is helping residents who were forced from their homes as officials work to determine the full extent of the damage.

The cause of the fire is still under investigation.