Brazilian Defense Minister Nelson Jobim has said there is no doubt a debris field found about 700 kilometers (435 miles) northeast of the Fernando de Noronha archipelago is from missing Air France flight AF447.

Earlier today searchers found an airplane seat, an orange life vest, small white fragments, an oil drum and signs of oil and kerosene 80 kilometers (50 miles) east of the plane’s expected flight path.

The announcement comes as commercial ships were expected to arrive to look for the Airbus A300-200 jetliner, which disappeared Monday with 228 people on board, four hours into an 11-hour flight from Rio de Janeiro to Paris.

According to Air France, the missing aircraft has built-in homing devices that may help searchers find it, but that could take up to a week.

Greg Feith, a former investigator with the U.S. National Transportation Safety Board, said homing devices such as “pingers,” which are underwater locator beacons attached to flight data and cockpit voice recorders, can transmit signals from as deep as 14,000 feet.

The average depth of the Atlantic Ocean is about 12,000 feet (3.66km).

“They’re water-activated, so if they’re sitting at the bottom of the ocean, of course, then the military assets will have to go in there with listening devices and try and home in on those particular signals.”

“What they’re going to have to do now is some reverse engineering, find out the location of this debris. Then they’re going to have to figure out what the tide speed was. It’s been around now for 28 hours. Now they’re going to have to back up that course probably several hundred miles to the actual area of the wreckage,” he added.

Air France flight AF447 departed Brazil’s Airport do Galeao in Rio de Janeiro on Sunday at 2230 GMT for Paris and was last heard from flying at an altitude of 10,600 meters (35,000 feet) at 0133 GMT Monday.

Air France have reported receiving one dozen automatically transmitted technical messages warning of multiple electric and pressurization failure over four minutes after it hit a storm mid-flight, however, no manual or automatic mayday message was received.