GEARHART, Ore. -- Investigators Tuesday said they believe the family inside a Gearhart home hit by a plane had approximately 20 seconds to get out before the house exploded into flames.

Residents of the quiet coastal resort and retirement community of Gearhart on the north Oregon coast are trying to piece together the hows and whys of a plane crash that ripped into the families of two daughters of a former Oregon attorney general.

One daughter was in the house Monday when a single-engine Cessna crashed into it. Another was on a walk with her husband.

Both daughters survived, but the crash killed three children -- grandchildren of Lee Johnson, a former legislator and judge who also was a two-term attorney general more than three decades ago.

More: Victim & survivor bios

The plane crashed in the fog Monday just after taking off. It touched off an explosion that rattled houses for a half mile. The pilot and his passenger died.

Firefighters said they found the bodies of two children inside the burned home and a third child was also confirmed dead. Those three children were identified as 8-year-old Grace Masoudi, 12-year-old Sam Masoudi and 10-year-old Julia Reimann.

Reimann's mother and two siblings were flown to a Portland hospital with serious injuries. Authorities said Ruth Reimann, 47, of Southwest Portland, rescued one of her children and her other surviving child climbed out a window. The two children who survived were identified as 11-year-old Sarah Reimann and 13-year-old Christopher Reimann.

Christopher jumped out of a window, officials said.

All three were being treated in the burn center at Legacy Emanuel Hospital. Specific details of their conditions were not released.

Relatives had rented the large vacation home for a family reunion. The parents of the two Masoudi children who perished were out walking with their oldest daughter when the crash happened. Witnesses said they became hysterical when they returned from their walk and saw the devastation.

Dr. Fred Masoudi, a cardiologist at Denver Health Medical Center, was on vacation with his wife, Dr. Marie Johnson and their three children.

Slideshows: Community in shock | Fire & crash scene

The pilot and a passenger who had been on board the plane when it crashed were missing and presumed dead. The pilot was identified as Jason Ketcheson and his passenger was identified as Frank Toohey, 58.

"This is the biggest thing that has ever hit Gearhart. It’s such a tragedy, everybody is devastated,” Gearhart City Administrator Dennis McNally said.

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Neighbors ran out into the streets of the small town and did everything they could to try and help after the huge explosion.

“People were yelling and screaming. It really was horrific,” a witness told KGW. "Everyone who saw this is pretty much in shock. The first house is just gone."

KGW photo

What's left of one of the homes after the plane crash.

The home next door, which turned out to be vacant, also caught fire during the explosion and parts of the plane were scattered in the back yards, witnesses said.

“Today is a sad and tragic day for our community,” said Mayor Ken Smith. “We are all deeply touched and saddened by today’s unfortunate events.”

Dawn Black, who lives nearby, told KGW she heard a noise that "sounded like a lawn mower puttering out" followed by a loud explosion. Then, when the plane crashed, "it felt like an earthquake." Her son, Drew ran outside and took photos of the fireball down the street and shared them with KGW.

Slideshow: Photos of plane crash scene | Email us Your photos

Investigators said the fiery explosion happened just after 6:30 a.m. when the plane first hit a tree, then the house. Emergency crews from three surrounding counties responded. It took about an hour to put out the flames.

Powerful explosion felt around town

Workers at a nearby golf course told KGW it knocked out their power. People living nearby said they heard a loud explosion and saw flames shooting into the sky.

The house was located at 398 N Marion Street. Federal aviation authorities reached the scene Monday afternoon and said the investigation could take weeks. The owner of the vacation rental house, Greg Marshall of Portland, told The Oregonian newspaper that the victims arrived Sunday for a planned two-week stay.

The plane had taken off at the Seaside Airport Monday morning en route to Klamath Falls. It was described as a Cessna 172. A check of the tail number confirmed that it had been rented from Aviation Adventures, out of Seaside for personal use.

m0a.com photo

An example of a Cessna 172.

More Cessna 172s have been built than any other aircraft and the four-seat, single-engine, high-wing airplane is probably the most popular flight training aircraft in the world, according to aircraft Web sites.

Blog: Dave Salesky blogs on the plane

Conditions in the area were very foggy when the crash happened, with low clouds, drizzle and light wind, which may have contributed to the crash.

The town of about 1,100 people has a mix of permanent and seasonal residents.