Missing Malaysia Airlines Flight MH370 was most likely brought down by a stowaway on board the jet, an aviation expert claimed over the weekend. The new theory comes just weeks after Malaysia said in its report that they have not ruled out the possibility of a hijack.

Philip Baum, editor of Aviation Security International, reportedly said that experts should be looking into the possibility that someone sneaked onto the Boeing 777-200 to sabotage the flight.

“I think a stowaway is a strong possibility, especially as no officials seem to want to even contemplate the possibility,” Baum told the Independent, adding he believes the saboteur likely hid underneath the floor or just behind the flight deck in a “hinged, self-closing access panel.”

Aviation Security International has previously reported as many as 123 stowaway attempts internationally across 107 separate flights.

The latest conspiracy theory emerges as France reopened its investigation into the disappearance of Flight MH370 after Malaysia's long-awaited report failed to explain what happened to the jetliner. The 449-page report that was released on July 30 sparked condemnation from the families of those on board the jet as they accused the Malaysian government of a massive cover-up.

The report stated Flight MH370 deviated from its path "not because of anomalies in the mechanical system. The turn back was made not under autopilot but under manual control.” Investigators could not "establish if the aircraft was flown by anyone other than the pilot."

Earlier, conspiracy theories claimed Captan Zaharie Ahmad Shah deliberately crashed the jet in the Indian Ocean as part of his "murder-suicide" plan. But Malaysia's report last month said Shah had no history of mental or psychiatric treatment, and that there was no evidence of conflict issues with friends or family, no drug use, no evidence of troubled relationships with family members.

Flight MH370 went missing on March 8, 2014, with 239 people on board while on its way from Kuala Lumpur to Beijing. A multimillion-dollar search for the missing plane yielded no concrete clues as to the plane's whereabouts.

The biggest lead in the investigation came when a plane flaperon was found by villagers on Réunion Island. Investigators said 27 pieces of wreckage are believed to be from MH370, though only three have been confirmed as parts belonging to that plane.

Since the plane went missing, there have been several theories that emerged related to the cause of the plane's mysterious disappearance. Some theorists claimed MH370 was shot down by military forces. While some claimed the plane was accidentally shot down during a joint U.S.-Thai military exercise, others blamed North Korea of doing so. Some theorists claimed the jet entered another Bermuda Triangle, also known as the Devil’s Triangle, located in Asia in the Indian Ocean.

There were also theories of a possible electrical issue resulting in a fire on board the plane, which probably caused the crew to pass out from smoke inhalation, and the plane continued on autopilot until it ran out of fuel, eventually crashing into the Indian Ocean.