Four people were killed Friday morning in a plane crash near Harrisburg north of Eugene, officials said.

The plane crashed before 11 a.m. in a field about a quarter mile from Peoria Road and about a mile outside Harrisburg, Linn County Sheriff Bruce Riley told The Oregonian/OregonLive.

"We don't know whether it's weather-related and or mechanical," Riley said.

There were no survivors aboard the single-engine plane, identified by the National Transportation Safety Board as a Piper PA-46.

Witnesses saw the plane flying low, the sheriff said.

"No indication of any issues other than it was flying a little low," Riley said. "That's what drew their attention to it -- that it was loud and low."

He also said, "Obviously with this weather and high winds that could easily be a contributing factor."

He said the names of the plane's occupants would not be released until after FAA investigators arrived and until family members had been notified.

Flightaware.com activity indicates the plane was headed to Eugene from Van Nuys Airport in Southern California's San Fernando Valley. The website indicates the pilot flew past the Eugene Airport before circling back.

The plane appears to be owned by Park City Aviation LLC in Utah.

Workers at Knife River Prestress, a Harrisburg concrete company, saw the plane crash from about two miles down Peoria Road.

Tom Walker, a general foreman at Knife River Prestress, said he was walking north in the company's yard when the sound of a low-flying plane caught his attention. He looked up and saw the plane flying just above the treeline.

"They were flying normal," he said. "All of a sudden, it flipped on its side, then headed straight down toward the ground in a nosedive."

Walker said he could still hear the plane's engine running as the plane tipped and fell.

"It was instantaneous," he said.

Knife River employee Jay Patel saw the falling plane through a window.

"I see this plane just plummeting," Patel said. "It was going straight down."

Patel and several others jumped into a truck and drove to the crash site, where they saw the plane wreckage. Patel said they nearly drove past the crash site because there was no smoke or visible fire.

It appeared the plane had hit the ground head-on, said Dusty Andrews, another of the workers and a volunteer firefighter for nearby Adair Village. All four occupants were deceased by the time they arrived, Andrews said.

They called 911 from the scene and said emergency responders arrived within minutes.

Winds were south to north at 20 miles per hour gusting to 30 mph at about 11 a.m. at the Eugene Airport, National Weather Service meteorologist Colby Neuman said. A light rain was falling.

The cloud ceiling was at 3,600 feet, with a "scattered ceiling" at 2,700 feet, adding that weather data at the time of crash has been shared with the FAA.

Riley described the crash scene as "locked down," awaiting the arrival of the FAA. The victims would be left in the plane until the federal investigators' arrival, he added.

NTSB investigating today's crash of a Piper PA-46 in Harrisburg, OR. — NTSB_Newsroom (@NTSB_Newsroom) April 7, 2017

A National Transportation Safety Board investigator was traveling Friday to the crash site from the agency's Seattle-area office, said NTSB spokesman Peter Knudson.

Early Friday evening, inspectors, including one wearing an NTSB jacket, were seen inspecting the plane and marking the scene with orange flags. A firefighter appeared to begin cutting into the cockpit of the plane.

The NTSB is the lead investigative agency in plane crashes and, working in conjunction with FAA investigators, will determine probable cause for the crash, Knudson said. The FAA supplies information such as pilot training records, pilot medical certification, aircraft records and air traffic control data, he said.

The FAA issued a brief statement about the crash, noting the site is five miles northeast of Mahlon Sweet Field Airport, the formal name for the Eugene Airport. FAA spokesman Allen Kenitzer declined further comment.

Eugene Airport spokesman Casey Boatman said the control tower reported a small plane approaching the airport about 10:50 a.m. had crashed about 10 miles north of the airport.

Boatman said preliminary information indicates the plane was approaching the airport from the north for landing.

Boatman said he was not aware of cancellations or delays in flights at the airport Friday because of high winds. Earlier Friday, two flights were canceled and two delayed at Portland International Airport.

The Piper PA-46 is known by the model name Malibu and "is a good airplane" that, depending on the year built, ranges from $250,000 to $1.1 million, said pilot Wayne Cartwright, who lives near Salem.

Cartwright, who is selling a 1990 Piper Malibu, said the Piper Malibu's retractable gear would be valuable if the pilot had been able to land wheels up in a field.

He saw little value in speculating now on the cause of the crash, however.

"All the guessing we can do right now doesn't mean a doggone thing," he said. "The story won't be available for months until the NTSB really figures out what happened."

Charles Davis of Ventura, California, and his wife heard the plane before the crash.

"I heard the plane flying low and then it wasn't too long after that, maybe seven or eight minutes, and we started hearing sirens," said Davis, 67, who is staying in their Winnebago at the Life Northwest RV park near Harrisburg.

"He's putting a lot of power in an airplane and he's low," Davis said he recalls thinking. "So why's he doing that? And the wind, it was just horrible right then."

The last fatal plane crash in Oregon was earlier this year, near Cape Blanco.

In 2012, four people were killed in a plane crash near Veneta.

-- Elliot Njus

enjus@oregonian.com

503-294-5034

@enjus

-- Andrew Greif

agreif@oregonian.com

@andrewgreif

--Allan Brettman

abrettman@oregonian.com

503-294-5900

@allanbrettman

News researcher Lynne Palombo contributed to this report.