Authorities say nobody was injured when a five-story Harlem townhouse collapsed Friday afternoon, spreading an immense cloud of debris through the area.

Emergency crews rushed to 110 West 123rd Street to find a massive pile of rubble.

First responders picked thought the pile in search of anyone trapped inside but found no sign that anyone had been in the building, which Department of Buildings officials say was undergoing renovations.

The building had recently been sold and last month the city's Department of Buildings issued a permit for work to structurally reinforce the building.

"It was like a big train hitting the house," said one man who witnessed the collapse. "It was just an enormous sound, just thunderous."

"I saw the smoke just coming to me," said another eyewitness. "And I didn't want to move 'cause I didn't know if the building was going to come straight on to me."

Real estate agent Jay Harper, who showed the building to a client in January, says the basement was reinforced with braces and that a contractor had told him he was "scared of the building."

Neighbors said it was a miracle that nobody was hurt in the collapse. Workers left the premises at around noon, only hours before the building came down.

A community garden next door was locked for the day, so nobody was working there when debris rained down over the area.

Department of Buildings officials say the building has no safety violations on file.