Malaysia Airlines flight MH370, which went missing over four years ago, was likely manipulated deliberately to take it off its route, investigators said in a report on Monday. The report did not rule out “unlawful interference by a third party”, according to Reuters.

Malaysia called off its search for MH370 on May 29. The aircraft vanished on March 8, 2014, when it was on its way to Beijing from Kuala Lumpur with 239 people on board. It is believed to have crashed in the southern Indian Ocean, hundreds of miles away from its scheduled route.

In a 495-page report, investigators said they were not able to determine who was responsible for the flight’s disappearance. “The answer can only be conclusive if the wreckage is found,” Kok Soo Chon, who headed the MH370 safety investigation team, said.

“We are not of the opinion it could have been an event committed by the pilots,” he said. However, he said the possibility could not be ruled out as the plane was turned around manually.

“The turn-back could not be attributed to an anomalous system,” said Kok. “It has been established that the air turn-back was done under manual control, not autopilot...we cannot rule out unlawful interference by a third party.”

Instead of giving answers, the report mainly disproved many theories about the aircraft’s disappearance, according to The Guardian. Kok said the investigators had looked into “over 60” allegations, theories and rumours that have surfaced over the last four years. “We removed them one-by-one and saw what remained behind,” he said.

The report found no signs that the plane was evading radar detection or that it had been taken over by remote control. No irregularities were found in the onboard cargo either.