"I heard a big boom, like the biggest boom I've ever heard," she said.
Another neighbor said his house shook.
Battalion Chief Dan Lipski from the Milwaukee Fire Department said there may have been an explosion.
"There was some type of event that shook the house off its foundation," he said.
The fire department and neighbors don't believe anybody was in the house. The owner was renovating, neighbors said. She bought the home from the city in June for $5,250. At the time, the city estimated it would need $22,000 in renovations.
The gas line to the house was off when the fire department arrived, two minutes after a 911 call.
"That leads us in another direction in our investigation," Lipski said.
Police arson investigators and the State Fire Marshall were at the home well into the evening. Other homes sustained minor damage.
The owner of the home declined to speak with TODAY'S TMJ4.