Surveillance aircraft searched a remote area of the southern Indian Ocean on Thursday for possible debris from the missing Malaysian passenger jet, after objects were spotted by an Australian satellite.
The searchers were hampered by poor visibility, but covered 23,000 square kilometers about 2,500 kilometers southwest of the western Australian city of Perth.
After numerous false leads in the 13-day search for the Boeing 777 with 239 people aboard, Australian Air Commodore John McGarry said the large objects spotted by satellite are a possible breakthrough.
"Quite simply, it is credible enough to divert the research to this area on the basis it provides a promising lead to what might be wreckage from the debris field."
A large number of ships and planes from several countries are also being diverted to the area to help in the search.
Australian officials said a number of images of possible debris were spotted four days ago, with one object about 24 meters long and another five meters long.
Australian Prime Minister Tony Abbott, who first announced the findings on Thursday, warned against making presumptions about the nature of the objects, saying it will be "extremely difficult" to locate them.
Australia has been helping coordinate the southern section of the search for the missing aircraft, which disappeared after taking off March 8 from Kuala Lumpur on an overnight flight to Beijing. At least 26 nations have been hunting for the plane across a search area covering more than seven million square kilometers.
Investigators believe someone with advanced knowledge of aircraft deliberately diverted the plane either south toward the Indian Ocean or north toward Central Asia. They have refused to rule out any possibility, including terrorism, pilot suicide, or a mechanical malfunction.
U.S. President Barack Obama on Wednesday said the search is a "top priority" for the United States. He told an American television station that he has put every available resource into the effort.