France announced Sunday that it had new satellite data showing possible debris from the missing Malaysia Airlines plane, the latest images to raise hopes of finding the jet.

On Monday morning, the search was set to expand to the area pinpointed by the French data, as two Chinese planes joined the Australian-led mission. But observers looking out from planes flying low over the area have not been able to see anything matching the objects picked up by various satellites.

The French images are the third set of satellite information issued in the past week that depict what could be wreckage from the plane that disappeared March 8 with 239 people on board.

The object seen by a French satellite was 528 miles north of the current search area, Australian Deputy Prime Minister Warren Truss said in an interview with ABC Radio, Australia’s national public broadcaster. The French Foreign Ministry said radar echoes from a satellite had indicated the presence of debris in the ocean about 1,400 miles from the Australian coastal city of Perth but gave no direction or date.

“We still don’t know for certain that the aircraft is even in this area,” Truss said in the interview. “We are just 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 Australian Maritime Safety Authority on Monday expanded the search once again, in light of the most recent sightings, with a total of 10 aircraft scouring two areas covering more than 42,500 square miles.

The hunt for the plane — which vanished while en route from Kuala Lumpur to Beijing — is one of the broadest aviation search-and-rescue operations in history.

Low fog hampered the search early Sunday, but John Young, general manager of the Australian maritime agency’s emergency response division, said weather conditions in the remote part of the Indian Ocean appeared to be improving.

The grainy satellite photograph of a “suspicious floating object” issued by the Chinese was taken about 75 miles southwest of the debris sighting announced by Australia last week. The photograph was dated March 18, two days after the images from Australia were released.

The Australian maritime agency said the Chinese image was “consistent” in size and location with the other images. It said its planes had passed over the area identified in the Chinese image Saturday without spotting anything.

The object spotted by the Chinese was 74 feet long and 43 feet wide. That is too wide to have come from a plane “unless it is the root of the wing,” said Peter Marosszeky, an aviation expert at the University of New South Wales in Australia. “It is a possibility, though unlikely.”

A Boeing 777-200 is 209 feet long, with a wingspan of 199 feet and a tail height of 60 feet above the ground. Its body is 20 feet in diameter.

Even if empty fuel tanks inside the wing were filled with air, some experts said they doubted a fragment of that size could stay afloat for 10 days.

Mike Barton, the rescue coordination chief at the Australian maritime agency, said the biggest challenge was the search area’s “remoteness from anywhere.” That meant search planes were operating at the limits of their fuel supply, prolonging the search, he said.

Satellites have the advantage of passing directly over an object, “but actually determining what it is from an aircraft at a lot lower altitude, looking into the sun, with haze and all the rest of it, is proving difficult,” Barton said.

If planes can find any of the floating objects or any new ones of interest, the next step will be to get a ship to the area and fish them out of the water. “Until we find them and have a good look at them, it’s hard to say if they have anything to do with the aircraft,” Barton said at a news conference in Canberra, the capital.

An Australian naval vessel is in the area, and a small flotilla of Chinese ships is heading to the search zone in the coming days. Merchant ships that had been involved in the search have been released, the Australian maritime agency said Sunday.

Japan and India were sending more planes, and two Chinese Ilyushin aircraft have arrived in Perth and are due to join the search Monday, the Australian agency said.

Young said the search area was being constantly refined to make it as accurate as possible.

On Sunday, the Malaysian government denied recent U.S. media reports that the passenger jet had been pre-programmed to turn sharply westward before it vanished from radar. Those reports, citing unidentified U.S. officials, said the plane’s last transmission through the Aircraft Communications Addressing and Reporting System, or ACARS, at 1:07 a.m. on March 8, indicated the shift in route, casting suspicion on the two pilots.

This was not true, Malaysia’s Ministry of Transport said in a statement. “The last ACARS transmission, sent at 1:07 a.m., showed nothing unusual,” it said.