PARIS (AP) _ A steady stream of flowers arrived Thursday at Paris' 18th century Madeleine church, where French and German officials joined weeping relatives and uniformed airline crews to pay tribute to the 113 victims of the Air France Concorde crash.

As about 1,000 people gathered for the memorial service, investigators said they had finished decoding the second black box from the Concorde supersonic jet that plowed into a hotel outside the French capital on Tuesday. It could take up to three more days to complete the analysis of the fatal flight, the Transport Ministry said.

The ministry said there were 600 pieces of undamaged technical information, such as speed and height, on the recovered flight data recorder. It has to be analyzed and compared with information gathered earlier from the other black box, the voice recorder.

A judicial and aeronautics expert said the loss of control points to a ruptured turbine blade as the cause of the fiery crash.

In central Paris, distraught relatives arrived at the church, and the building began filling up with somber-looking crew members in the crisp, blue uniforms of Air France, including some bearing the winged insignia of Concorde cabin crews. Tourists mingled with Parisians for a moment of quiet reflection before the start of the memorial for the victims, most of whom were German.

Jean Leprovost, a visitor from France's northern Normandy region, stopped by to pay his respects.

``It was a catastrophe. What can you say?'' Leprovost said. ``Everybody was affected by this all around France, even in the small villages.''

President Jacques Chirac, who did not attend the service, sent a large bouquet of pale pink roses and other flowers. Other more modest bouquets came from ordinary Parisians who wanted to show their sympathy.

Air France, which has promised to compensate victims' families, said Thursday it would pay an advance of $20,000 each to help cover immediate outlays, like funeral costs.

Elsewhere Thursday, workers finished removing the bodies of all 113 victims from the charred and blackened crash site and transferring them to a morgue in Paris for the difficult process of identification. Also, the French prosecutor's office in the Val d'Oise region opened an inquiry into ``involuntary homicide and involuntary injury,'' judicial sources said on condition of anonymity.

Such an inquiry can call witnesses and last for months. It will look at whether to bring charges and against whom. Involuntary homicide is defined as a negligent killing punishable by up to three years in prison.

The ministry has ruled out sabotage and said it doesn't appear to be pilot error, so the inquiry would likely focus on maintenance or mechanical problems.

French authorities trying to determine what turned the sleek delta-winged jet into a furnace that dropped from the sky were focusing on the mighty Rolls-Royce engines that power the world's fastest jetliners at twice the speed of sound across the Atlantic. Officials said the fire that consumed the Concorde seconds after its takeoff from Charles de Gaulle airport probably started in the No. 2 engine.

The investigation should focus on turbine blades that rotate and compress air inside both engines on the left wing, including the No. 2 engine, Raymond Auffray, an engineer and aeronautics adviser to Paris' Court of Appeal, said in the La Croix newspaper Thursday. Auffray's office is not connected to the inquiry.

The lack of control of the aircraft signals a ruptured turbine blade, Auffray said, which would cause the engine to destruct. The risk of such a rupture in normal circumstances is less than one in a billion for each hour of flight, so Auffray did not exclude the possibility of ``intruding objects'' in the engine.

Air France said mechanics had worked on engine No. 2 just before the takeoff. But government officials said it was too early to say if the repairs were linked to the accident.

Le Figaro, meanwhile, reported investigators were not ruling out the possibility of human error. The Liberation daily also cited Andre Turcat, a longtime supersonic pilot, as saying the pilot's decision to head toward nearby Le Bourget airport instead of returning to Charles de Gaulle was ``imaginable but risky.''

Capt. Christian Marty tried to wrestle his stricken jet down on Le Bourget airport as a fiery blaze was consuming the left side of the plane, said Elisabeth Senot, the prosecutor in charge of the judicial investigation.

Video shot by the wife of a Spanish truck driver from a nearby highway captured the disaster. Like a monstrous, wounded bird, the great white plane struggled to gain height as a bubbling, blazing spout of flame and black smoke bellowed behind.

The plane dived into the Hotelissimo in Gonesse, a gritty industrial suburb north of Paris, killing all 100 passengers, nine crew members and four people in the hotel.

Ninety-six of the victims were Germans heading for the vacation of a lifetime _ supersonic jet to New York, then a five-star cruise into the Caribbean, through the Panama Canal to Ecuador and, for some, a trans-Pacific voyage to the Olympic Games in Sydney, Australia.

Their deaths, which ended the Concorde's 31-year record of safe flying, united France and Germany in sadness and provoked speculation about the jetliner's future.

For more than a quarter-century, Britain and France boasted of the plane they jointly developed as a marvel ahead of its time. But Concorde has never been a commercial success. Before the crash only 13 were operated _ seven by British Airways, six by Air France.

All Air France Concorde flights have been grounded since the crash. Transportation Minister Jean-Claude Gayssot said Wednesday he hopes to authorize them to start again soon.

British Airways resumed Concorde flights from London to New York on Wednesday after initially canceling services following the crash.