“The plane is presumed to have crashed in the far southern Indian Ocean.

PUTRAJAYA — A Malaysian-led independent investigation report released Monday, more than four years after Malaysia Airlines Flight 370 disappeared, highlighted shortcomings in the government’s response and raised the possibility of “intervention by a third party.”

The report, prepared by a 19-member international team, reiterated Malaysia’s assertion the plane was deliberately diverted and flown for over seven hours after severing communications.

Chief investigator Kok Soo Chon said the cause of the disappearance cannot be determined until the wreckage and the plane’s black boxes are found. He said there was no evidence of abnormal behavior or stress in the two pilots that could lead them to hijack the plane but all passengers were also cleared by police and had no pilot training.

“We are not of the opinion that it could be an event committed by the pilot,” Kok told a media briefing.

“We cannot rule out unlawful interference by a third party,” such as someone holding the pilots hostage, he said. But he added that no group has said it hijacked the plane and no ransom demands have been made, compounding the mystery. Kok said it was up to police to investigate.

He said the investigation showed lapses by air traffic control, including a failure to swiftly initiate an emergency response and monitor radar continuously, relying too much on information from Malaysia Airlines and not getting in touch with the military for help.

The plane carrying 239 people from Kuala Lumpur to Beijing vanished 8 March 2014 and is presumed to have crashed in the far southern Indian Ocean. The report said there was insufficient information to determine if the aircraft broke up in the air or during impact with the ocean.