The search for Malaysia Airlines Flight 370 has resumed in a desolate stretch of the Indian Ocean, more than six months after the passenger jet vanished.

The Malaysian-contracted GO Phoenix vessel arrived in the area on Monday to begin its underwater search, scanning the ocean floor for the plane, the Australian Transport Safety Bureau (ATSB) said.

The search has been on hold for four months so crews could map the seabed in the search zone, about 1,800km west of Australia.

Given the unknown nature of the ocean floor in that area, since found to include extinct volcanoes, sheer ridges and deep trenches, a bathymetric survey to map the seabed was considered vital before an underwater search could start.

Australia has been spearheading the hunt for the plane which is believed to have hit the ocean after mysteriously diverting off-course from Kuala Lumpur to Beijing and running out of fuel.

The Boeing 777 went missing on March 8 with 239 people on board.

'Seventh arc'

The 60,000-square kilometre search site lies along what is known as the "seventh arc" - a stretch of ocean where investigators believe the aircraft ran out of fuel and crashed.

Officials analysed transmissions between the plane and a satellite to estimate where it entered the water.

Two other ships being provided by Dutch contractor Fugro are expected to join the GO Phoenix later this month.

The ships will be dragging sonar devices called towfish through the water about 100 metres above the seabed to hunt for the wreckage.

The towfish are also equipped with sensors that can detect the presence of jet fuel, and are expected to be able to cope with the depths of the search zone, which is 6.5km deep in places.

If anything of interest is spotted on the sonar, crews will attach a video camera to the towfish to film the seabed.

Expressing cautious optimism that the plane will eventually be found, Martin Dolan, ATSB's chief commissioner, said: "We're confident in the analysis and we're confident that the aircraft is close to the seventh arc."

Source: Agencies