Last Updated Apr 10, 2014 2:07 PM EDT
The Australian air force P-3 Orion, which has been dropping sonar buoys into the water near where four earlier sounds were heard, picked up a "possible signal" that may be from a man-made source, said Angus Houston, who is coordinating the search off Australia's west coast.
"The acoustic data will require further analysis overnight,"
said in a statement. Houston