PERTH, Australia – A Chinese plane on Monday spotted a white, square-shaped object in an area identified by satellite imagery as containing possible debris from the missing Malaysian airliner, while the United States separately prepared to send a specialized device that can locate black boxes.
The crew aboard an IL-76 plane sighted the object in the southern Indian Ocean and reported the coordinates to the Australian command center, which is coordinating the multinational search, as well as the Chinese icebreaker Snow Dragon, which is en route to the area, China's Xinhua News Agency reported.
From 10,000 meters (33,000 feet), the spotters saw two larger floating objects and some smaller, white debris scattered over several square kilometers (miles), the report said. It gave no other details.
Satellite images released by Australia and China had earlier identified possible debris in the area that may be linked to the disappearance of Malaysia Airlines Flight 370 on March 8 with 239 people aboard.
The U.S. Pacific command said it was sending a black box locator in case a debris field is located. The Towed Pinger Locator, which is pulled behind a vessel at slow speeds, has highly sensitive listening capability so that if the wreck site is located, it can hear the black box pinger down to a depth of about 20,000 feet (6,100 meters), Cmdr. Chris Budde, a U.S. Seventh Fleet operations officer, said in a statement.
"This movement is simply a prudent effort to preposition equipment and trained personnel closer to the search area so that if debris is found we will be able to respond as quickly as possible since the battery life of the black box's pinger is limited," Budde said.
There was no sign the move was linked any break in the mystery of the plane, but rather as a preparation.
The Chinese plane was one of two Ilyushins that joined the search Monday from Perth, increasing the number of aircraft to 10 from eight a day earlier.
The Australian Maritime Safety Authority said the objects spotted Monday were "within today's search area and attempts will be made to relocate them."
Bad weather was threatening the search efforts in the area, about 2,500 kilometers (1,550 miles) southwest of Perth. Australia's Bureau of Meteorology reported increased winds, low cloud and a reduction in visibility on Monday. On Tuesday, a cold front was expected to move through the search area from the west, bringing showers, more low cloud and less visibility. Tropical Cyclone Gillian, which is further to the north, will not impact the area.
Australian Transport Minister Warren Truss said "nothing of note" was found Sunday, which he described as a "fruitless day."
"It's going to be a challenge, but we'll stick at it," he told Australian Broadcasting Corp. radio. "We're just, I guess, clutching at whatever little piece of information comes along to try and find a place where we might be able to concentrate the efforts."
The search was given added momentum when a French satellite detected potential debris on Sunday, after Australia and China earlier released satellite images identifying suspect objects.
Australian authorities had sent planes and a ship to try to locate a wooden pallet that was spotted on Saturday from a search plane, but the spotters were unable to take photos of it.
Wooden pallets are most commonly used by ships but are also used airplane cargo holds, and an official with Malaysia Airlines said Sunday night that the flight was, in fact, carrying wooden pallets. The official spoke on condition of anonymity in keeping with company policy.
In Paris, French Foreign Ministry spokesman Romain Nadal said in an interview with The Associated Press that the satellite radar echoes "identified some debris that could be from the Malaysian Airlines plane."
The spokesman said that these echoes "are not images with a definition like a photograph, but they do allow us to identify the nature of an object and to localize it."
Gathering satellite echo data involves sending a beam of energy to the Earth and then analyzing it when it bounces back, according to Joseph Bermudez Jr., chief analytics officer at AllSource Analysis, a commercial satellite intelligence firm.
Satellite radar echoes can be converted into an image that would look similar to a black-and-white photo, though not as clear, he said. "You'd have to know what you're looking at," Bermudez said.
A Malaysian official involved in the search said the French data located objects about 930 kilometers (575 miles) north of the spots where the objects in the images released by Australia and China were located.
One of the objects located was estimated to be about the same size as an object captured Tuesday by the Chinese satellite that appeared to be 22 meters (72 feet) by 13 meters (43 feet), said the official, who declined to be identified because he wasn't authorized to speak to the media.
U.S. underwater wreck hunter David Mearns on Monday described the French satellite sighting of potential debris as a "positive development," although he was unaware of the full details.
Mearns was an adviser to British and French search authorities following the loss of Air France Flight 447 in the Atlantic Ocean during a flight from Brazil to Paris in 2009.
He warned that time was running out to find confirmed wreckage that could lead searchers back to the aircraft's black box.
The southern Indian Ocean is thought to be a potential area to find the jet because Malaysian authorities have said pings sent by the Boeing 777-200 for several hours after it disappeared indicated that the plane ended up in one of two huge arcs: a northern corridor stretching from Malaysia to Central Asia, or a southern corridor that stretches toward Antarctica.
Malaysian authorities have not ruled out any possible explanation for what happened to the jet, but have said the evidence so far suggests it was deliberately turned back across Malaysia to the Strait of Malacca, with its communications systems disabled. They are unsure what happened next.
Authorities are considering the possibilities of hijacking, sabotage, terrorism or issues related to the mental health of the pilots or someone else on board.
In the U.S., Tony Blinken, President Barack Obama's deputy national security adviser, said on CNN: "There is no prevailing theory."
"Publicly or privately, we don't know," he said. "We're chasing down every theory."
McDonald reported from Kuala Lumpur, Malaysia. Associated Press writers Rod McGuirk in Canberra, Australia, Todd Pitman and Eileen Ng in Kuala Lumpur, Kristen Gelineau in Sydney, Ian Mader in Beijing, Cassandra Vinograd in London, and Elaine Ganley and Oleg Cetinic in Paris contributed to this report.