The crash happened in the 600 block of Burmont Road near Bloomfield Avenue just before 1 p.m.
The helicopter was traveling from WellSpan Chambersburg Hospital in Chambersburg, Pennsylvania to Children's Hospital of Philadelphia when the incident occured.
The three crew members were rushed to Lankenau Medical Center and the two-month-old infant patient was taken to CHOP. Officials said, miraculously, no one suffered life-threatening injuries.
"It's a miracle. It's an absolute miracle," said Upper Darby Police Superintendent Timothy M. Bernhardt.
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There have been no reports of any injuries to people on the ground.
A witness, Joshua James, said he was driving nearby with his wife and young son when he saw the tail of the helicopter swaying back and forth as it slid to a stop. He put his car in reverse.
"It makes no sense to me that it didn't hit any of the wires or anything - that it didn't hit us," James told the Associated Press.
Actions News spoke with residents on the block who said the helicopter was several feet from their homes before it crash landed.
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"The noise was so loud I thought it was a bomb. It was crazy, not a sound I've ever heard before," said Lisa Smith.
Neighbors then flooded the streets.
"I ran out down the street, there were flames and people climbing out from the top of the helicopter," said Denise Palmarino who's lived in Drexel Hill for 20 years.
Everyone is praising the pilot, who was in a very tough spot. There are a lot of homes, a busy road, schools, and businesses surrounding the scene of the crash.
"I can't wait to meet this gentleman and shake his hand for getting this (helicopter down) the way he did," said Bernhardt.
Emma Gray, an Upper Darby High School senior, was traveling in a Lyft vehicle when she heard the crash nearby.
"We heard this big boom. All of a sudden there was a bunch of glass and flaming debris on the road. Then there was a helicopter and part of it was on fire," she recalled.
Gray said she and her Lyft driver got out to help.
"These guys started coming out of it and they're like, 'Someone come help us, there's someone trapped underneath.' They were like, 'here take this,' to my Lyft driver, and it was a baby," recalled Gray.
Gray said she did her best to calm the pilot.
"I was able to kneel down beside him and say like, 'Hey man, I called 911, help is in the way," said Gray.
A statement from WellSpan Chambersburg Hospital said "...earlier today a LifeNet medical helicopter based out of Hagerstown, Md. That flight subsequently crashed on the way to Philadelphia. Our hearts go out to family and crew on board and we are grateful that early reports indicate the patient and crew survived and that the patient was transported on to the planned hospital by ground transport."
A fire official said the helicopter had about an hour's worth of fuel left at the time of the crash, and crews took steps to keep leaking fuel from contaminating groundwater.
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The Federal Aviation Administration said the aircraft was a Eurocopter EC135 medical helicopter and that the agency was investigating, along with the National Transportation Safety Board.
A spokesman for Air Methods, the air medical emergency transport service that owns the helicopter, said it was part of the LifeNet program based in Hagerstown, Maryland. Federal agencies were investigating.
"Our team will cooperate fully with their efforts to assess the cause of this unfortunate accident," said Air Methods spokesman Doug Flanders.
A cause of this crash remains under investigation.