Australian co-ordinators in the search for a missing Malaysian plane say a Chinese ship has detected a pulse signal for a second time, within hours of it being heard earlier on Saturday.
Air Chief Marshal Angus Houston called the discovery in the southern Indian Ocean an “important and encouraging lead”.
He warned that the data were still unverified.
British naval ship HMS Echo is sailing to the area to investigate further.
It is expected to arrive in the early hours of Monday.
Australian aircraft were also on their way, Air Chief Marshal Houston told reporters. Australian naval vessel Ocean Shield would be heading to the latest search area once it had investigated a third acoustic detection elsewhere.
Both HMS Echo and ADV Ocean Shield have technology able to detect underwater signals emitted by data recorders.
Malaysia Airlines flight MH370 disappeared on March 8 with 239 people on board. Investigators believe it crashed in the Indian Ocean although no confirmed debris has been found. The battery-powered signal from the “black box” recorders fades after 30 days.