A fire in Newark, New Jersey completely burned through a home where six people died early on Sunday.

CNN reported that the fire began around 4 am. A source in Essex County, Chief of Detectives Anthony Ambrose, told CNN that arson investigators were looking into what caused the blaze.

It was reported that a woman lived at the house along with her daughter and two grandchildren, although the victims of the fire have not been named. Ambrose said the fire’s cause was still not known.

The Los Angeles Times reported that city officials told them the victims included four adults and two children.

Neighbors said the firefighters could do nothing to save the victims inside the house, the Newark-Star Ledger reported. The flames were moving too fast for the firefighters to be able to get inside the house to save the family.

One neighbor, Mark White, said, “That’s the hurting part, standing here and being helpless.”

While firefighters were able to get inside to fight the flames, they weren’t able to get to the residents.