A robotic submarine searching for any sign of the missing Malaysia Airlines jet resurfaced early for the second time in two days on Wednesday.
Officials blamed a “technical issue” for Bluefin-21's premature return from the deep off Australia's west coast.
The unmanned sub had been expected to search for 16 hours but one search on Tuesday ended after just six hours when a safety feature kicked in as the vessel exceeded its "operation depth limit" of 14,763 feet --or about 2.8 miles.
Australia’s Joint Agency Coordination Center, which is leading the search for Flight MH370, did not explain Wednesday's technical problem or reveal how long the sub had been able to scan the southern Indian Ocean before the mission was aborted.
The U.S. Navy-owned Bluefin-21 can create a three-dimensional sonar map of the area to chart any debris on the sea floor.
Authorities said data downloaded and analyzed from Bluefin-21's initial search on Wednesday highlighted “no significant detections.”
The vessel was later redeployed.
The acoustic search has been focused an area about the size of a medium city - around 230 square miles - and say it could take the underwater robot months to scan and map the whole search zone.
On Monday, officials announced that the air search for signs of the missing Boeing 777 would be called off within 72 hours. The jet vanished on March 8.