The full story may never be known, but Malaysian government investigators say they now believe they’ve pieced together a part of the MH370 mystery. A new report states the Malaysia Airlines plane’s controls were likely deliberately manipulated in order to take it off course—but it doesn’t say with certainty who did it or why. The plane vanished with 239 people on board en route to Beijing from Kuala Lumpur on March 8, 2014. “The answer can only be conclusive if the wreckage is found,” Kok Soo Chon, head of the MH370 investigation team, told reporters. “We are not of the opinion it could have been an event committed by the pilots,” he said, but added they were not ruling out any possibility. “We cannot exclude that there was an unlawful interference by a third party.” The only traces of the aircraft have been three wing fragments that washed up along Indian Ocean coasts.