Police are investigating four possibilities as to why Malaysia Airlines Flight MH370 has gone missing.

Inspector-general of police Khalid Abu Bakar said these are terrorism, sabotage, psychological problems and personal problems of passengers and crew.

Despite having established that one of two imposters who boarded the ill-fated flight had no terrorist links, Khalid refused to say that terrorism is now a less likely cause.

"There is same weightage to all (aspects) until we complete our investigation," he said.

Asked to elaborate that he means by "personal problems" of passengers and crew, Khalid said an example of the possibility is insurance fraud.

"There may be somebody on the flight who has bought a (substantial) insurance (policy and) who wants the family to gain from it or (there could be someone) who owes a lot of money," he said.

Khalid said the authorities are not ruling out mechanical or pilot failure, but said these aspects were being handled by the Department of Civil Aviation (DCA).

‘Five passengers not boarding MH370 is wrong’

Aside from scanning the CCTV recording of passengers, Khalid said cops were also studying the photographs and footage of the plane’s cargo.

Malaysia Airlines Flight MH370 carrying 227 passengers and 12 crew from Kuala Lumpur to Beijing on March 7 had disappeared from radar over the Gulf of Thailand about an hour after take-off.

To date, a search involving 32 aircraft and 40 ships around the waters where the plane disappeared has proved futile.

In a separate development, Khalid denied reports that there were five passengers who did not board the ill-fated flight, which has raised suspicion.

“Nobody who booked the flight did not board the plane... there was only one girl who called to cancel her booking because she mixed up the date,” he said.

When it was pointed out that this was a contradiction to the information released by the DCA, he replied: “"You take it from me, there was no such thing.”

Meanwhile, in a statement issued this evening, Malaysia Airlines clarified that four passengers did book for Flight MH370 but did not turn up.

“Malaysia Airlines wishes to clarify that there were four passengers who had valid booking to travel on flight MH370, March 8, 2014, but did not show up to check-in for the flight.

However, the airlines said as the four did not show up at all, the issue of their baggage supposedly being loaded on the Flight MH370 did not exist.

“As such, the issue of off-loading unaccompanied baggage did not arise, as the said four passengers did not check in for the flight. Hence, the above claim is untrue,” it said.