Dozens of ships and aircraft from seven countries scoured the seas for a Malaysia Airlines jetliner that went missing on Saturday.

But rescue equipment is lying idle, as the search has failed to find a confirmed trace of the aircraft or the 239 people.

Investigators are looking at all angles, including a possible terror attack or hijacking.

The focus has been on two passengers who boarded the flight using stolen passports.

Many of the passengers on the flight were from China. Beijing urged Malaysia to step up the search.

(SOUNDBITE) (Mandarin) CHINESE FOREIGN MINISTRY SPOKESMAN QIN GANG SAYING:

"We cannot confirm at present who it really was who misused these two passports. As I just said, China's public security ministry has already sent a dedicated inspection team to Malaysia to investigate this together with Malaysian side."

Thai police and Interpol are also helping with the investigation as the passports had been stolen in Thailand during