Fire officials pulled two people out of a small plane Monday morning after it crashed into a reservoir in Colorado.

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Authorities were called around 7:45 a.m. to the Culver Reservoir, about 50 miles north of Denver. A small-engine plane carrying two people crashed into the reservoir, according to the Berthoud Fire Protection District.

Ambulances took the pair to a hospital for treatment. Authorities did not identify either person or the extent of their injuries.

Video footage of the crash site showed the plane partially submerged near the shore of the reservoir as divers inspected the aircraft.

Federal aviation officials told The Denver Post that it was not immediately clear where the plane, a Cessna 172, was headed. It was also unclear where the flight originated.

Allen Kenitzer, a spokesman for the Federal Aviation Administration, told The Post that the crash happened under "unknown circumstances."

"This is all of the information we have at this time," he said.

The FAA and the National Transportation Safety Board are investigating the crash.