(CNN) Authorities have discovered the crashed wreckage of a small Cessna airplane after it failed to return to Billings, Montana, Saturday evening as planned.

Investigators are working to determine how many passengers were aboard the 1978 model Cessna 182 when it went down, Yellowstone County Sheriff's Office Capt. Kent O'Donnell told CNN. He added that it was a private, recreational flight.

The FAA and the NTSB are also investigating the crash, which is estimated to have occurred around 6 p.m. (8 p.m. ET) about 25 miles north of Billings, FAA spokesman Allen Kenitzer said. As of Sunday afternoon the circumstances surrounding the crash were unknown.

The initial alert notice for the search of the missing aircraft was issued shortly after 3 a.m. local time (5 a.m. ET) Sunday, he said, and the wreckage was located around 10 a.m. (12 p.m. ET).

Officials kicked off a search by air and ground at sunrise Sunday morning when the aircraft failed to return to Billings, O'Donnell said.

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