Jeff Riley of Seafloor Systems displays a sonar image of the the airplane wreckage in Folsom Lake.
CNN  — 

Workers testing underwater surveying equipment say they found the wreckage of a small airplane deep underwater in California’s Folsom Lake -— and they may have solved a 56-year-old aviation mystery.

Sonar images show the outline of the plane, covered in a thick layer of silt, about 160 feet below the lake’s surface, Seafloor Systems environmental technician Jeff Riley told CNN.

Riley said they first realized that something might be down there when they were going through data that his colleague Tyler Atkinson had collected while testing a small, unmanned surveying boat. Seafloor Systems, based in Shingle Springs, California, is a surveying company that specializes in mapping marine areas like lakes and ponds.

It was able to detect the wreckage because water levels at Folsom Lake are low because of the extreme drought conditions plaguing much of the Western United States. The lake is located about 25 miles northeast of Sacramento.

“I saw something that was not normal,” Atkinson told CNN affiliate KOVR.

They went back to the area with a small remote controlled mini sub, or ROV, but couldn’t get a good look because visibility was only about six or seven inches, Riley said.

The wreckage is about 160 feet underwater in Folsom Lake.

The team mounted a sonar unit on the ROV and went back again earlier this week Riley said, and when they got down to the bottom the wreckage “was as clear as day.”

“I did a little pan around just to see my surroundings, and in that initial pan I was able to see it,” Riley said.

They were able to collect images of the tail section of the plane and the propeller, and Riley said they appeared to match the description of a plane that crashed in 1965.

A Piper Comanche 250 crashed into the lake on New Year’s Day after a midair collision, according to KOVR.

The pilot’s body was recovered, but authorities never found the plane or the three passengers who were on board, KOVR reported.

Authorities tried to find the plane in 2014, but were unsuccessful after a three-day search, CNN affiliate KCRA reported.

Riley said that Seafloor Systems collected the GPS coordinates of the wreckage to help with a possible recovery effort.