Malaysian police have searched the homes of the pilots of the Malaysia Airlines plane that vanished eight days ago with 239 people on board.
The police are also reportedly looking at family life and psychological state of pilot Zaharie Ahmad Shah, 53, and co-pilot Fariq Abdul Hamid, 27.
This comes after the authorities said the communications systems of the plane had been deliberately disabled.
The Kuala Lumpur-Beijing flight is believed to have then changed course.
According to satellite evidence, the Boeing 777 could have continued flying for a further seven hours after its last radar contact, Malaysian Prime Minister Najib Razak said.
He added that the plane could be anywhere from Kazakhstan to the Indian Ocean.
Razak stopped short of saying it was a hijacking, saying only that they were investigating “all possibilities”.
In a separate development, India on Sunday suspended its search for the plane around the remote Andaman and Nicobar Islands and also in the Bay of Bengal.
Delhi said it acted at the request of the Malaysian authorities.
China – which had 153 citizens on board flight MH370 – has urged Malaysia to continue providing it with “thorough and exact information” on the search.
The Kuala Lumpur homes of Zaharie and Fariq were searched on Saturday, a senior police officer familiar with the investigation was quoted as saying by Reuters.
“We are not ruling out any sort of motivation at the moment,” the official said.
The authorities have so far released no new details on the pilots’ investigation.
However, nothing has been ruled in or out – so terrorism, piracy or even an elaborate suicide are all options now being considered, the BBC’s Jonah Fisher in Kuala Lumpur reports.
Zaharie joined Malaysia Airlines more than 30 years ago, and was considered a very experience pilot.
Fariq recently recently graduated to the cockpit of a Boeing 777. It is believed that he was considering marriage.