PARIS, France (CNN) -- The jet carrying 228 people from Rio de Janeiro, Brazil, that disappeared overnight as it entered an area of strong turbulence probably crashed into the Atlantic Ocean, the CEO of Air France said Monday.



Anne and Michael Harris, who lived in Rio de Janiero, Brazil, were two Americans aboard the flight.



Brazilian and French ships and planes were looking for any sign of the missing plane, authorities said.



The first three hours of what was to have been an 11-hour flight appear to have been uneventful, CEO Pierre-Henri Gourgeon said.



But about 4:15 a.m. Paris time, Flight 447's automatic system began a four-minute exchange of messages to the company's maintenance computers, indicating that "several pieces of aircraft equipment were at fault or had broken down," he said.



"This succession of messages signals a totally unforeseeable, great difficulty," he said. "Something quite new within the plane."



During that time, there was no contact with the crew, Gourgeon said.



"It was probable that it was a little bit after those messages that the impact of the plane took place in the Atlantic," he added.



He said the Airbus A330 was probably closer to Brazil than to Africa when it crashed.



He noted that turbulence made flying "difficult" in the area but that it is "too early to say" exactly what happened.



The chances of finding any survivors were "very low," French President Nicolas Sarkozy admitted Monday.



"This is a catastrophe the likes of which Air France has never seen before," he said at Charles de Gaulle International Airport, where he met with relatives of the missing.



"I said the truth to them: The prospects of finding survivors are very low," he said.



The airline company identified the nationalities of the victims as two Americans, an Argentinean, an Austrian, a Belgian, 58 Brazilians, five British, a Canadian, nine Chinese, a Croatian, a Dane, a Dutch, an Estonian, a Filipino, 61 French, a Gambian, 26 Germans, four Hungarians, three Irish, one Icelandic, nine Italians, five Lebanese, two Moroccans, three Norwegians, two Polish, one Romanian, one Russian, three Slovakian, two Spanish, one Swedish, six Swiss and one Turk.



An official list of victims by name was not available late Monday.



The American victims were identified as Michael Harris, 60, and his wife, Anne, 54, by the couple's family and his employer, Devon Energy in Oklahoma -- the largest U.S.-based independent natural gas and oil producer. Michael Harris was a company geologist in Rio de Janeiro, according to a company spokesman.



Anne Harris' sister, Mary Miley, told CNN the couple had been living in the city since July 2008 and that they were traveling to Paris for a training seminar for Michael and for a vacation.



"Anne and Mike were indeed a beautiful couple inside and out and I miss them terribly already," Miley said in an e-mail.



Sarkozy said French authorities sent ships and planes to the area about 250 miles (400 kilometers) from Brazil. "Our Spanish friends are helping us; Brazilians are helping us a lot as well."



French Transport Minister Jean-Louis Borloo told CNN affiliate France 2 that France asked the U.S. military to assist in the search through U.S. detection satellites. Pentagon officials in Washington did not immediately confirm the request.



Brazilian President Luiz Inacio Lula da Silva told reporters in San Salvador, El Salvador, that he had spoken with Sarkozy but neither leader knew what to say. "All we could do was thank each other," Lula said. "He thanked me for the speed with which the Brazilian air force took charge."



He added, "In times like these, there is little to do but to deeply lament, to wish the families a lot of strength, because there are no words in times like these."



Sarkozy said authorities were seeking the help of satellites that might
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