Investigators are examining the phone call made to Captain Zaharie Ahmad Shah, the pilot of the missing Malaysia Airlines flight MH370, a few hours before take-off from a fake number.
The phone number, from which the phone call was made, was bought under the stolen identity of a woman, Malaysian authorities told Mail Online.
The telephone conversation, between Shah and the unidentified person before the flight, lasted for about two minutes and it was one of the last conversations.
The authorities appear to be giving much weight to the phone call as it was made from an unknown pay-as-you-go SIM card number in Malaysia.
Meanwhile, the investigators are also trying to examine Shah's family including his estranged wife Faizah Khan. Though separated, she shares the same roof with Shah. She has not been approached by the police for the past two weeks, but the Malaysian authorities are increasingly under pressure from FBI officials to question her.
"Faizah has been spoken to gently by officers but she has not been questioned in detail to establish her husband's behaviour and state of mind in the days leading to the incident. This is partly for cultural reasons. It is not considered appropriate in Malaysia to subject people in situations of terrible bereavement to the stress of intensive questioning," a source told Mail.
Shah and his co-pilot have been under intense scrutiny soon after it was established that there was foul play in the mysterious disappearance of the plane.
Experts are also studying Shah's flight simulator for clues.