PASSAIC, N.J. (CBSNewYork) — A multi-alarm fire tore through an apartment building in Passaic County early Saturday afternoon.

Authorities say the flames broke out on the 5th floor of the building on Gregory Avenue and Pennington Avenues at around 1 p.m. The fire quickly spread to all 46 units in the building, causing multiple collapses, CBS2’s Jessica Borg reported.

“As we were operating, we realized the fire was getting well ahead of us. We were able to get up in there and try to get guys on the roof. We started opening up — fire was well advanced past any stage of possibly putting it out,” Passaic Fire Dept. Chief Patrick Trentacost said. 

It took more than 150 firefighters four hours to get the six-alarm fire under control, 1010 WINS’ Andrew Falzone reported. Officials say the heat was so intense at one point, firefighters had to leave the building.

More than 100 residents were left without a home.

Genesis Rivas said her mother lost everything in the blaze.

“Everybody says it’s just material, but at the end of the day, it’s everything you’ve worked so hard for,” Rivas said. “My mom’s retired, she’s older, so it’s not like she say ‘oh I’m going to work back up and get my life back started again.”

“It’s awful. It’s memories. I grew up in that building and to see my parents crying because they lost absolutely everything,” Carla Bravo said. “It’s sad.”

Tenants in the building say at first they weren’t sure if it was a false alarm — claiming the fire alarm goes off frequently.

“She stayed in bed for a while and somebody knocked on the door saying, ‘Let’s go, there’s a fire.'” resident Pedro Ramirez said.

For now, displaced residents are being sheltered at a nearby high school gymnasium. Many families ran out out of the burning building while in the middle of preparing their Easter meals.

“Obviously, this is a difficult time, but in this time as so many count their blessings, and look to their faith, the greatest blessing is that we don’t have a single loss of life,” Passaic Mayor Hector Lora said.

Trentacost said he believes the building is structurally sound, but there was substantial damage on the fourth and fifth floors, as well as the roof of the building.

Authorities said if the fire had started on the first floor, the whole building could have collapsed.

The cause of the fire is under investigation.