PORTLAND, Ore. (KOIN) – A search effort led on Thursday hopes to find new evidence in the only unsolved airplane hijacking in U.S. history: the D.B. Cooper case.

A small search team led by amateur investigator Eric Ulis searched a “treacherous” tree-and blackberry-lined trench where it is believed Cooper’s parachute may have been dumped.

The search comes 52 years after a plane heading to Seattle was hijacked by the man whose trace was never seen again.

New information was recently revealed by the Seattle air traffic controller who managed the skyjacked Northwest Orient Flight 305, two US Air Force F-106 chase jets, and an Oregon Air National Guard T-33 during the 1971 skyjacking.

Ulis says the trench is near the location where money connected to the heist was found in 1980. The cash was found on the banks of the Columbia River west of downtown Vancouver by 8-year-old Brian Ingram, who discovered $20 bills with serial numbers traced to Cooper’s ransom, a total of $5,800.

“It is clear to me that DB Cooper actually landed much closer to the 1980 money find spot than originally believed,” Ulis said. “I am absolutely certain that the heavy parachute DB Cooper jumped with is still near where the man landed 52 years ago.”

He added “we are searching in the correct area and will find the parachute.”

The results from Thursday’s search will be presented during next month’s CooperCon in Seattle.