The home was engulfed by the flames Tuesday evening in the 700 block of Southard Street, and is now at the center of a suspicious death investigation.
A man's body, who neighbors believe was the homeowner, was found inside the piles of debris.
One fire official called the home a "hoarder" house, making it impossible for first responders to get inside.
Firefighters battle raging 3-alarm fire in Trenton, New Jersey
"Everything was piled almost to the ceiling," said Deputy Chief Cliff Willever.
Investigators from the Mercer County prosecutor's office arson unit were at the scene with dogs combing through the property.
"There was a big explosion early on and that caused it to go to both buildings," Willever said.
Charred items from inside the home were left on the sidewalk.
According to neighbors who did not wish to speak on camera, the home's occupant lived alone but would get an occasional visit from a relative.
Neighbors also tell Action News that the home next door, which was also damaged in the fire, was known to authorities. It's still unclear if that home is part of the ongoing investigation.