Firefighters arrived at 9:56 p.m. Friday and encountered the heavy blaze in the rear of a small wood-frame residential structure at 15 Emerson Ave.
Fire chief Alex Alicea said the strong winds fueled the quick spread of the fire onto the second level of the one-and-a-half-story structure, where the five victims were found, two adults and three children.
The flames were so intense the heat melted the siding of the house next door.
The Passaic County Prosecutor's Office said the adult victims were a 39-year-old male and a 38-year-old female, and the three children were ages 14, 12 and 7.
There seven other residents living in the home, including a girl with special needs, survived but have been displaced. The Red Cross is assisting those families.
"Our disaster volunteers were at the scene and assisted three people in two families with emergency assistance to help with temporary lodging, food, clothing, and other immediate needs," the Red Cross said in a statement. "We expect to provide emergency assistance to an additional four people who requested that we meet with them later today."
Neighbors were stunned by the devastation, telling Eyewitness News that some residents who escaped the blaze and lived on the first floor tried to save the victims but could not navigate the stairs, which were ablaze.
As the fire quickly spread, a neighbor made an effort to use a garden hose to try and suppress the flames.
John Miller, a neighbor, described the victims as very friendly.
"They were really good people, friendly. Every time I'd drive by, they would always wave," Miller said. "To hear about this, it's unbelievable."
The Paterson school district will have grief counselors available for students on Monday.
The cause of the fire remains under investigation.
This is a developing story. Check back for updates.