A medical transport flight carrying five passengers apparently broke apart midair before crashing in Nevada on Friday night, killing everyone aboard, including a patient, officials said Sunday.

The single-engine Pilatus PC-12 aircraft is believed to have broken up before crashing into the ground in a mountainous area near Stagecoach, Nevada, after investigators found debris from the plane nearly a mile away from the crash site, the National Transportation Safety Board (NTSB) said.

"How do we know if the airplane broke up in flight? We found parts of the airplane one-half to three-quarters of a mile away," NTSB Vice Chair Bruce Landsberg said during a news briefing.

The aircraft was en route from Reno, Nevada to Salt Lake City according to the NTSB. The Federal Aviation Administration said the plane, which was built in 2002, was registered to Guardian Flight.

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NTSB investigators examining wreckage

The medical air transport flight, operated by Guardian Flight, crashed on Feb. 24 while enroute from Reno, Nevada, to Salt Lake City. (National Transportation Safety Board )

Care Flight, a service of REMSA Health in Reno and Guardian Flight, identified the downed aircraft and said the pilot, a flight nurse, a flight paramedic, a patient and a patient’s family member all died.

NTSB investigators examining wreckage

The pilot, a flight nurse, a flight paramedic, a patient and a patient’s family member all died in the crash, according to Care Flight, a service of the plane's operator, Guardian Flight. (National Transportation Safety Board )

Poor weather and visibility were reported at the time of the crash. 

The National Weather Service had issued a winter storm warning issued in Reno for large swaths of Nevada, including parts of Lyon County. It was snowing steadily with winds around 20 mph and gusts up to 30 mph.

NTSB investigators examining wreckage

NTSB investigators documenting the wreckage of a Pilatus PC-12 airplane at the crash site in Dayton, Nevada.  (National Transportation Safety Board )

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Visibility was under two miles with a cloud ceiling about 2,000 feet above the ground when the flight left Reno for Salt Lake City and went down, according to the weather service.

NTSB investigators canvassing mountainous area

Debris from the aircraft was found strewn up to three-quarters a mile away from the crash site, raising the likelihood the plane broke apart midair, NTSB said. (National Transportation Safety Board )

An NTSB team is investigating the wreckage to determine a possible cause of the fatal crash.

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"Right now, we just don't know. This is like a three-dimensional puzzle," Landsberg said. "It's harder when you don't have the pieces all in one place."

The Associated Press contributed to this report.