Investigators looking for missing Malaysia Airlines flight 370 are making a final sweep of the search area in the Indian Ocean before the operation concludes in January.

Australia's Joint Agency Coordination Center said one of the last search vessels is due to revisit sites of previous sonar contact in the 120,000 square kilometer area of sea bed.

China has ended its involvement in the search, although it will continue to take part in briefings. Search teams have been working for 1,000 days, but no trace of the aircraft has been found.

However, authorities have found three pieces of MH370 debris on beaches in Mauritius, Tanzania and the French island of Reunion. Investigators are examining several other items found in Mozambique and South Africa.