A partial collapse inside an Upper East Side brownstone Friday sent four construction workers to the hospital.

It happened inside a home under construction at 222 East 62nd Street.

Fire officials say the roof was removed and workers were in the process of adding a fifth floor to the structure when the third and fourth floors partially gave way.

"They were doing some work on a rear wall, which is the backyard. They have some scaffolding set up there and they were removing some brick. In the process of removing some of the brick to put in a steel lintel. The entire rear third wall collapsed onto them," said FDNY Chief Thomas McKavanagh

"So I came outside all of a sudden a bunch of firefighters came out and they went inside the building and 20 minutes later they puled out someone on a stretcher who had a neck brace around his neck," said Olivia O'Driscoll, a neighborhood resident.

Three construction workers were sent by ambulance to the hospital; a fourth showed up on his own.

Their injuries are all said to be non-life threatening.

The city Department of Buildings is investigating.