All five people aboard an airplane died when the plane crashed in a field northwest of the main runway at Erie Municipal Airport on Sunday.

The single-engine plane crashed while coming in for a landing at about 11:50 a.m., said National Transportation Safety Board investigator Courtney Liedler. She confirmed Sunday afternoon that all the passengers died. Their names and ages are being withheld by the Weld County Coroner’s Office pending notification of relatives.

The six-passenger plane, a Piper PA-46 based out of Erie, is registered to Real Estate School LLC. The company is owned by real estate lawyer Oliver Frascona, who lives in Erie’s Air Park neighborhood.

Two of the passengers on the plane were taken to area hospitals after the crash, including one who was airlifted by a medical helicopter based at the airport, according to Erie police. A dog on board also died in the crash, according to Mountain View Fire Rescue.

Liedler said the pilot was flying in from the Centennial Airport. The crash investigation is still in its preliminary stage and no causes have been ruled out, she said, adding that the investigation will look at “the man, the machine and the environment.”

The morning’s weather was warm and clear, though witnesses reported windy conditions. The MesoWest website monitored by the University of Utah showed a relatively calm, sustained wind speed of 12 mph with “breezy” 18-mph gusts at the time of the crash.

Jan Culver said she was with a friend in a pasture near the airport when she heard the sound of a plane and looked up to see one flying “really, really low.”

“We heard it sputtering,” she said. “Then there was no sound. We knew it was a crash.”

She said she saw a small cloud of dust as the plane crashed and, because she has some medical knowledge, went to the scene to help.

“It was a plane upside down with some folks already out of the plane,” she said. “I could tell there were some bad injuries.”

She said she didn’t have the right equipment to help the victims, but “you should always try.”

“It’s very hard,” she said. “Somebody passed today.”

Mountain View Fire Rescue, the Lafayette Fire Department and Erie police all responded to the crash. Liedler, with the NTSB, said the aircraft’s manufacturer is expected to be on scene Monday to assist. Once the investigation at the site is complete, the wreckage will be taken to another location for a thorough examination, she said.

NTSB records show the Erie Airport was the scene of three crashes in 2013 and two in 2012. None of those incidents had a fatality.

The last fatality at the airport was in May 2011, when 64-year-old Christian R. Hansen crashed on takeoff in a plane he was demonstrating for a potential buyer. His son was watching from the ground.

The autopsy indicated Hansen had a heart attack.

The Denver Post contributed to this report.

Contact Camera Staff Writer Amy Bounds at 303-473-1341 or boundsa@dailycamera.com.