Bystanders rushed to help those onboard the Cessna 206 after it clipped the roof of a motel and crashed in front of an unoccupied former car lot office, sparking a fire, shortly after 5 p.m. No other injuries were reported.
"It was the citizens who did the work and pulled people out," said police Lt. Dave Parker.
A witness, Hunter Brosh, said a girl about 10 years old was among those pulled out alive. Brosh was one of the motorists who jumped out of their cars to help get people out of the burning plane.
Parker said at least one of the injured was flown to a Seattle hospital.
The identities and hometowns of those onboard were not yet known, said Jennifer Rodi, a National Transportation Safety Board investigator. The single-engine plane was registered to Cavner and Julian Inc., a guide and outfitting business based in Port Alsworth, Alaska. No one with the business could be reached for comment Tuesday night.
Rodi said it was too early to say what caused the crash.
The aircraft went down after departing Merrill Field about a mile away. Rodi said it was unknown who was flying the plane or if a flight plan had been filed.
She said the four survivors were critically injured. However, Brosh said the girl onboard was able to unbuckle herself before she was helped out of the wreckage.
One witness, Adan Hernandez, said he was riding his bicycle when he heard the plane above him. The aircraft started to wobble before disappearing beyond the motel and making a thudding sound, said Hernandez, who took photos of the crash site. A small, cone-shaped piece of the aircraft landed in the motel's parking lot.
Brosh was driving to a guitar lesson and had stopped at a nearby intersection when he heard a loud noise behind him. He swung his head back as the plane slammed into the ground. People started to pour out of their cars and run to the aircraft.
Brosh said the plane burst into flames while those on board were still being extricated.
People starting running over with fire extinguishers. At one point, Brosh heard some of those helping exclaim, "You're spraying on the baby."
A man and a woman onboard appeared very hurt, he said. The woman's mouth was full of blood and it appeared her teeth were knocked out, he said.
For Brosh, the experience was an "adrenaline thing," he said, as he stood outside the yellow police tape used as a barricade.
"I can't say I've ever helped people out of a burning plane," he said.