It’s been two years since Malaysia Airlines Flight MH370 vanished with 239 people on board. Investigators believe the aircraft crashed in the vast Indian Ocean, and an initial search of a 23,000-square-mile area of seafloor has been expanded to another 23,000. But little evidence has turned up since the plane’s mysterious disappearance, leading many to spin conspiracy theories.

The Beijing-bound Boeing 777 vanished from radar March 8, 2014, while flying over the Indian Ocean, shortly after taking off from Kuala Lumpur, Malaysia. A confirmed piece of the plane’s wing was found on the French Indian Ocean island of Réunion, on the other side of Madagascar, on July 2015. An object that could also be debris recently washed up on the shores of Mozambique and will be taken to Australia to determine whether it belongs to the missing plane.

Hijacked by Terrorists

Some people speculate that the Malaysian jetliner was hijacked by terrorists. Russian newspaper Moskovsky Komsomolets reported in April 2014 that the plane had been taken over by unknown terrorists and flown to Afghanistan, where the crew and passengers are being held captive. The newspaper also claimed the passengers and crew were divided into groups and living in horrid conditions with almost no food.

The bizarre report cited an alleged Russian intelligence source, who apparently told the newspaper: "Flight MH370 Malaysia Airlines missing on March 8 with 239 passengers was hijacked. Pilots are not guilty; the plane was hijacked by unknown terrorists. We know that the name of the terrorist who gave instructions to pilots is ‘Hitch.’ The plane is in Afghanistan not far from Kandahar near the border with Pakistan."

Other theorists believe terrorists hijacked the plane and crashed it into the sea, after the revelation that at least two of the passengers on board were traveling on stolen passports. But Malaysian officials said the two men had no apparent links to terrorist groups, according to BBC News.

Fire

One popular theory is there was a fire on board MH370, possibly electrical or from an overheated tire on takeoff, that killed all passengers and crew. However, theorizers believe it burned out before damaging the plane’s exterior, which is why the aircraft flew such a long distance off course while on autopilot.

Greg Feith, a former crash investigator for U.S. National Transportation Safety Board, has disputed the theory, saying there should have been a distress call in the case of a fire; no such call was received.

"Typically, with an electrical fire, you'll have smoke before you have fire," he told NBC News in March 2014. "You can do some troubleshooting. And if the systems are still up and running, you can get off a Mayday call" and pilots can put on an oxygen mask, Feith said.

Shot Down

In his book “Flight MH370: The Mystery,” London-based journalist Nigel Cawthorne claims the missing plane was accidentally shot down during a joint Thai-U.S. military training drill, based on the eyewitness testimony of a New Zealand oil rig worker, Mike McKay. McKay told Cawthorne he saw a burning plane go down in the Gulf of Thailand, shortly after MH370 stopped communicating with air traffic controllers on March 8, 2014. Cawthorne says the missing plane is now the subject of a massive international cover-up, the Independent reported.

Meanwhile, former Proteus Airlines CEO Marc Dugain has claimed the U.S. Air Force, fearing another Sept. 11 terrorist attack, shot down the Boeing 777. Dugain said in December 2014 he believed the plane was being controlled by a remote hacking, which caused it to veer off course while traveling between Kuala Lumpur and Beijing. He claimed MH370 was likely flying past a U.S. military base located on the remote island of Diego Garcia when it was shot down, the U.K. Daily Star reported.

U.S. Military Base

There were also rumors the commercial plane could have landed at the U.S. military base on Diego Garcia, located some 2, 175 miles from Malaysia. However, the U.S. government has flatly denied the claims, according to the Mirror.

"There was no indication that MH370 flew anywhere near the Maldives or Diego Garcia,” a spokesman for the U.S. Embassy in the Malaysian capital reportedly told the local Star newspaper by email in April 2014. "MH370 did not land in Diego Garcia."

Suicide

Another widely held theory for the sudden disappearance is pilot suicide. But so far, no evidence has suggested either Capt. Zaharie Ahmad Shah or co-pilot Fariq Abdul Hamid had such intentions. Hugh Dunleavy, the commercial director of Malaysia Airlines, said Shah was a seasoned pilot with a pristine record.

"There have been absolutely no implications that we are aware of that there was anything untoward in either his behavior or attitude," Dunleavy told Reuters in March 2014. "We have no reason to believe that there was anything, any actions, internally by the crew that caused the disappearance of this aircraft."

A Second Bermuda Triangle

Some theorists even believe the jet entered another Devil’s Triangle located in Asia in the Indian Ocean. A number of aircraft and ships are said to have disappeared under mysterious circumstances in the patch of sea in the North Atlantic Ocean known as the Bermuda Triangle, or Devil’s Triangle.