The cell phone of the 27-year-old co-pilot of the MH370 plane was switched on, and he tried to make a call to the mobile phone tower in Penang.
CNN was told that the signal of the phone was tracked from where it was sent, and the cell was searching for service about half an hour after the aircraft made a sharp turn towards the west.
According to the NST, the first officer attempted to call the tower while the plane was on the move.
But the US official familiar with the missing-plane investigation said that the Penang tower did not pick up any signal from other cell phones.
In the meantime, US Navy submersibles are searching for the plane beneath the surface of the southern Indian Ocean.
According to officials, the search could take up to two months to scan the whole search area.
On Sunday evening, the Ocean Shield, an Australian ship, detected an oil slick. A two-litre sample was collected for examination, but experts will take a couple of weeks to analyze it.
In a search on Monday, about 15 ships and 12 planes were used. They covered an area of 47,600 square kilometres.