Multiple 911 calls came in around 12:45 a.m. from the 100 block of Hemlock Court at the Narraticon Apartments.
Initial reports came in of a back porch on fire.
When crews arrived, they said there was heavy fire coming from the rear of the complex.
"It's all wood frame. It's all vinyl siding on the side, which is -- it's petroleum, and then once it gets up in a cock loft, it went left and right," said Deptford Fire Chief Richard Thomas. "Fire got big -- got big fast."
The chief said residents helped stretch some of the hose from the first engine.
"The issue is for us, for the fire department -- the fire was in the back of the building, and the asphalt that you're seeing here will not sustain the fire truck. Probably would have gotten 100 feet and sunk, so that's why you see the trucks outside, and we stretched all the hand lines in. Took a little bit to get hand lines stretched. Once we got water, we knocked it down, but it was already in the building," Thomas said.
Action News viewers sent in video as flames shot through the roof of the building.
"The fire was 50 feet in the air, if not higher," Thomas said.
One neighbor was reading when she heard noises.
"I was nosy, and I peeked out of my back patio door, and I was like, 'Is somebody setting off fireworks out there?', and I said, 'No, no,' that's a fire,'" explained Melissa Dwornick.
Additional crews from neighboring towns were also called in to help.
At one point, firefighters had to be pulled back from the building after the second floor collapsed.
Nine units were damaged and one person sustained minor smoke inhalation, but refused medical treatment. No firefighters were injured.
The cause of the fire remains under investigation. The Red Cross was called in for assistance.