Speedboats whisked French navy divers to the site of an Indian Ocean plane crash to search Monday for the black boxes belonging to Yemenia Airways Flight 626.

A 12-year-old girl was the sole survivor when the plane carrying 153 people plunged into the sea early Tuesday as it tried to land in the Comoran capital of Moroni in darkness and high winds.

Yemenia says it is too early to know the cause of the crash but critics have accused the airline of using a substandard plane after it emerged a 2007 French safety review found the Airbus 310 had a number of safety faults.

French military spokesman Christophe Prazuck said the divers had not yet located the two black boxes that will help solve the controversy but had heard signals emitting from them. The cases carrying the flight data and cockpit voice recorders are believed to be lying between 1,600 to 4,000 feet (500 to 1,200 meters) under the surface of the ocean, he said.

Prazuck said France is also sending a research boat, the Beau Temps Beau Pres, with detailed navigational tools that can help map out the ocean floor and locate the boxes. The boat, normally based in Djibouti, won't arrive until next week. French underwater robots to help retrieve the boxes are expected July 12.

Answers can't come too soon for anxious relatives like Fahad Mohamed, whose half-brother was aboard the plane. He criticized the Comoran government for keeping families waiting for news hours after the plane went missing and for broadcasting conflicting reports on survivors.

"We are hurting because we do not know anything. Where are our relatives?" he demanded angrily. "We don't know whether he's dead. Right now he's just lost. Getting lost is not the same as being dead."

The tightly knit islands have been hit by a roller coaster of elation and despair, due mostly to the survival of 12-year-old Bahia Bakari and the subsequent failure to find any more survivors.

Jean Youssouf, director-general of El Maarouf Hospital in Moroni, says around half of the country's villages have lost a resident. Weddings have been canceled, restaurants are refusing to play music for tourists and a pair of billboards by the airport proclaim the country's mourning.

To visitors, the country is an idyllic island, where sun-drenched fishermen haul silvery nets aboard battered dhows and the smell of cocoa, vanilla and ylang-ylang crops drift down lush volcanic foothills to glittering blue and white beaches.

But the country's beauty belies decades of political instability and poverty — its annual per capita income is about $300 — and now some residents feel their lives have been valued too cheaply.

Yemenia pulled the fatal aircraft from French skies in 2007 after its safety problems were flagged, but continued to operate it between Yemen and Comoros, where safety standards are less stringent and passengers are often poorer.

France did not inform the Comoros of the airline's safety problems.

"Why ban (the planes) for the French, but not ban them the Franco-Comorans?" Comoros Vice President Idi Nadhiom asked last week.

Around 15,000 demonstrators converged on the airline's French offices this weekend and the airline announced it was closing its Paris-Comoros route for months — until at least September. Yemenia was considered one of the cheaper international airlines on that route.

Sixty-six French citizens were aboard the plane, many French-Comorans coming home for summer vacations.

Ali Abou Abasse, a senior Comoran police officer coordinating the search and rescue site at the coastal town of Mistamiouli, said it was not clear how long investigators would need to locate the boxes.

Abasse also said so far no bodies have been recovered from the crash site, off the northern end of the main island of Comoros, an archipelago of three main islands 1,800 miles (2,900 kilometers) south of Yemen off the southeast coast of Africa. It is a former French colony.

For Mohamed, the most difficult part is not knowing whether his half-brother will ever be found. He says until his family has a body, they cannot carry out important rituals such as the 40 days of mourning required under Islam.

"We will have to wait," he said.