FOUR people have been killed after a small plane crashed, the Federal Aviation Administration has confirmed.

The twin-engine Cessna P337 crashed at about 9.40am on Sunday in a heavily wooded area in Boulder, Colorado.

Four people were killed after a small plane crashed in Colorado on Sunday

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Four people were killed after a small plane crashed in Colorado on SundayCredit: KUSA
The fire sparked a wildfire that led to evacuation warnings from officials

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The fire sparked a wildfire that led to evacuation warnings from officialsCredit: Denver 7

The crash sparked a wildfire in the Lefthand Canyon area, as reported by KDVR.

It caused authorities to issue an evacuation warning for surrounding areas.

All passengers were killed, according to the Boulder County Sheriff's Office.

However, officials have not revealed a cause for the crash.

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The identities of the victims also remain unknown.

Investigators have not yet been able to closely inspect the aircraft due to heat within it from the fire, per 9News.

The fire caused by the crash burned about a half acre in heavy timber before it was controlled.

The evacuation warning was lifted at around 11.40am.

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"The reporting party saw the plane crash into the ground and then reported smoke and flames in the area," the sheriff's office said in a statement.

"Firefighters arrived on the scene and reported a single-engine plane that had been destroyed."