SYDNEY - A deep-water search of the Indian Ocean for the missing Malaysian Airlines flight MH370 will begin in September, the Australian authorities announced on Friday.

The plane, carrying 239 people on board, disappeared without trace over the southern Indian Ocean on March 8 and has triggered widespread search efforts off the west coast of Australia.

Australia's Joint Agency Coordination Centre (JACC) said two ships, Zhu Kezhen and Fugro Equator, have continued to work in the southern Indian Ocean, surveying the sea floor where the plane is believed to have crashed in preparation for the deep-sea search.

"The aim is to identify significant features on the sea floor, which may present a hazard for the deep-water vehicles that will be used for the search," JACC said in a statement.

In June, an expert satellite working group identified a search zone of up to 60,000 square kilometres, which represents the highest priority for future search efforts. It is located along the seventh arc, a thin but long line that includes all the possible points where the last known communication between the aircraft and a communications satellite could have taken place.

JACC said the Zhu Kezhen, a Chinese PLA-Navy vessel, has sounded over 25,000 square kilometres along the seventh arc and Fugro Equator, an Australian-contracted specialized survey vessel, has covered over 43,000 square kilometres. This month, a Malaysian survey vessel, the KD MUTIARA, joined the search efforts.