In order to retrieve the data recorder, two ships with locator capabilities are searching a 240km (150 mile) underwater path.
Angus Houston, head of the Joint Agencies Coordination Centre (JACC) leading the search, said that two ships had commenced the sub-surface search for emissions from the black box pinger, the BBC reported.
Australia's search chief said it was a race against time as the battery-powered signal fades after 30 days
The former military chief, who is now coordinating the eight-nation search, said it was getting pretty close to the time when it might expire.
The Malaysia Airline plane that went missing on 8 March en route from Kuala Lumpur to Beijing is believed to have crashed in the southern Indian Ocean.
However, no confirmed debris has been found from the plane yet.