A doctor in the Comoros told Reuters a child had been plucked alive from the sea and was being taken to a medical center. The manager of the international airport in Moroni said the child was five. He said five bodies had also been found.
The Paris airports authority said 66 French nationals were aboard the plane, which was flying the final leg of a trip from Paris and Marseille to Comoros via Yemen.
A Yemeni aviation official said there were also nationals from Canada, Comoros, Ethiopia, Indonesia, Morocco, the Palestinian territories, the Philippines and Yemen on the plane.
Two French military planes and a French ship left the Indian Ocean islands of Mayotte and Reunion to search for the plane.
A doctor from the military hospital aboard one of the rescue boats called the Mitsamiouli hospital to tell them a child had been rescued alive, Halidi Ahmed Abdou, a doctor at a medical center opened for survivors, told Reuters.
It is the second Airbus to plunge into the sea this month. An Air France Airbus A330-200 crashed into the Atlantic Ocean killing 228 people on board on June 1. A preliminary report on that crash is due on Thursday.
The Paris-Marseille-Yemen leg of the Yemenia flight was flown by an Airbus A330. In Sanaa, those passengers who were flying on to the Comoros changed onto a second Yemenia plane, the A310 that crashed.
French Transport Minister Dominique Bussereau said faults had been detected during inspections in France in 2007 on the Yemenia A310, and that it had not flown to France since.
The A310 in question was inspected in 2007 by the DGAC (French transport authorities) and they noticed a certain number of faults, he told the I-tele television channel.
The company was not on the black list but was subject to stricter checks on our part, and was due to be interviewed shortly by the European Union's safety committee.
But Yemen's transport minister said the plane was thoroughly checked in May under Airbus supervision.
It was a comprehensive inspection carried out in Yemen ... with experts from Airbus, Khaled Ibrahim al-Wazeer told Reuters from Sanaa. It was in line with international standards.
The EU's Transport Commissioner Antonio Tajani said it would contact Yemenia to see what had happened and planned to propose a global blacklist of airlines deemed unsafe.
French television showed pictures of friends and relatives of the passengers weeping at Paris's Charles de Gaulle airport, many of them railing at the airline.Airbus said it was dispatching a team of investigators to the Comoros. It said the aircraft was built in 1990 and had been used by Yemenia since 1999. Its engines were built by Pratt and Whitney, a unit of United Technologies.
We still do not have information about the reason behind the crash, or survivors, Mohammad al-Sumairi, deputy general manager for Yemenia operations, told Reuters.
A Yemenia official said there were 142 passengers including three infants, and 11 crew. The plane was flying to Moroni, capital of Grande Comore, the main island of the archipelago.
The weather conditions were rough; strong wind and high seas. The wind speed recorded on land at the airport was 61 kph (38 mph). There could be other factors, Sumairi said.
We think the crash is somewhere along its landing approach, said Ibrahim Kassim from ASECNA, an aviation security agency which covers Francophone Africa. The weather is really not very favourable. The sea is very rough.
The French military said it had sent army and civilian medical teams, boats and divers to the crash site aboard the plane from Reunion. Comoros authorities sent small speedboats.
France and the Comoros have enjoyed close ties since the islands' independence in 1975. France estimates 200,000 people from Comoros live in mainland France, and remittances from France are an important part of the islands' economy.
A United Nations official at Moroni airport, who declined to be named, said the control tower had received notification the plane was coming in to land, and then lost contact with it.
Yemenia is 51 percent owned by Yemen and 49 percent by Saudi Arabia. Its fleet includes two Airbus 330-200s, four Airbus 310-300s and four Boeing 737-800s, according to its website.
The Comoros comprises three small volcanic islands, Grande Comore, Anjouan and Moheli, in the Mozambique channel, 300 km (190 miles) northwest of Madagascar and a similar distance east of the African mainland.
(Additional Richard Lough in Antananarivo, Inal Ersan in Dubai, David Clarke in Nairobi, Pascal Lietout, Anna Willard, Thierry Leveque and Guy Kerivel in Paris; Writing by David Clarke; Editing by Dominic Evans)