An underwater sonar device, scouring the southern Indian Ocean floor for missing flight MH370, has been lost for a second time this year.

The "towfish" was lost on March 21 after a tow cable connecting it to the Dong Hai Jiu 101 search ship failed, the Joint Agency Coordination Centre said in its weekly statement.

The Chinese-flagged ship is en route to Western Australia's Fremantle Port while a team assesses recovery options for the sonar device.

Another towfish was temporarily lost in January after it crashed into a 2200-metre mud volcano.

Wednesday's statement also confirmed possible aircraft debris - thought to be the cowling or the covering of its engine - has been found in South Africa.

The Malaysian Government is now working with South African officials to arrange for examination of the debris.

Meanwhile, two pieces of debris found in Mozambique arrived in Canberra for testing on Sunday.

The Boeing 777 went missing in March 2014 with 239 people on board.