The exact cause is still being determined, but senior officials believe actions by the driver will end up being the cause.
The driver may have been distracted, or his foot may have gotten stuck between pedals.
"Thank God that nobody got killed," neighbor Corey Demetrio said. "It literally went through somebody's house."
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The B49 bus was traveling southbound on Bedford Avenue when the driver lost control, jumped a curb and crashed into the building.
An initial investigation found "no mechanical defect" caused the crash, and it appeared the bus "was not going at a high rate of speed," MTA officials said.
"Most of the patients were ambulatory meaning they self-evacuated from the bus, or they were assisted off by the fire department members," FDNY Deputy Chief James Smithwick said. "We went through the building to make sure they were nobody trapped inside under the debris, and we and we told everybody they had to evacuate the building and they were just taking out through regular arrangement. Nobody was taken out on ladders or anything."
The 55-year-old driver, who has been on the job for 13 years, wasn't seriously injured. Officials say he has no major safety record infractions, only minor collisions.
The bus remains in the brownstone at 174 Lincoln Road Tuesday, after the Department of Buildings determined the structural stability is compromised and the building is no longer safe to occupy.
Caroline Petties is a super at a building down the block.
"Lucky we got bricks, because if it was made of wood, they would have been dead," she said.
Crews had hoped to remove the bus from the building later Tuesday, but due to structural concerns, it appeared the bus would remain until at least Wednesday.
The Buildings Department says before the bus can be removed, the building owner must install shoring to prevent a potential collapse.
All residents in the building have been offered emergency relocation assistance.
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