PARIS: French investigators said Saturday that the Air France jet which plunged into the Atlantic suffered multiple systems failures in its final moments and had speed monitors that had failed on other planes. Skip related content

Automatic error messages broadcast by the Airbus A330 just prior to the crash on Monday showed that its autopilot had cut out after it received conflicting speed readings, the head of the French air accident investigation agency said.

"We have seen a certain number of these types of faults on the A330," BEA director Paul-Louis Arslanian told reporters, confirming the missing jet had had a problem calculating its speed on the flight from Rio de Janiero to Paris.

"There is a programme of replacement, of improvement," he said, adding that planes that have not yet had replacement speed monitors are not necessarily dangerous, and that in other cases pilots had been able to regain control.

Arslanian said that the plane sent 24 automatic error messages in its final moments as its systems -- including the autopilot -- shut down.

It was impossible to tell from the signals whether the doomed crew had shut off the autopilot or whether it cut out, he added.

On Friday, Airbus urged all pilots of its jets to review a warning issued in July 2001 on the procedures to follow if speed indicators give conflicting readings and force the autopilot to cut out.

Investigators seeking clues to what had caused flight AF 447 to crash with 228 people on board have so far had to rely on the automatic messages as salvage crews have been unable to locate the wreckage in deep Atlantic waters.

Brazilian air force spotters believe they have identified floating debris, but no surafce vessel has been able to recover any, and a French nuclear sub and a research ship equipped with mini-submarines are steaming to the scene.

Early speculation as to the cause of the accident focused on foul weather, as the jet was flying through a thunderstorm, but Arslanian said the conditions had not been exceptional for the region.

He also played down the idea that a terrorist bomb might have destroyed the plane, saying that the 24 error messages showed the onboard electronic systems including the autopilot had shut down one by one.

But he did not formally rule out an attack: "Really, that would be truly astonishing, but that's not to say it is 100 percent impossible."

Meanwhile, intense search operations continued 1,000 kilometres (600 miles) off Brazil's northeast coast, as salvage teams attempted to locate the black box flight recorders which might solve the mystery.

Five more Brazilian navy vessels were already in the area, which was being overflown by 12 Brazilian and French aircraft, and the French submarines and research vessel were heading to the area.

The head of air traffic control for the area, Brazilian Brigadier Ramon Cardoso, told reporters "we have not made any recovery of material."

Some items spotted floating in the vicinity were "not relevant," he said, adding that weather conditions were terrible, limiting visibility, and currents had changed direction.

Brazilian officials said items picked up Thursday turned out on closer inspection to be nothing more than trash, probably from ships.

Cardoso said the objects spotted from planes might have since sunk to the bottom of the ocean, where the plane's black boxes are also believed to be.

While the investigation cast about for clues, families of those on board the plane expressed frustration with the lack of physical evidence that their loved ones were gone forever.

A group of 10 Brazilian relatives were flown from Rio to the main search operations centre in the Brazilian city of Recife on Friday to speak to a pilot involved in the search for the plane.

They left without speaking to media, and returned to Rio where another service was held in memory of the Air France passengers and crew.

An investigation into the previous accident showed it was caused when the Australian A330's flight computer gave incorrect information to the autopilot, causing the plane to plunge into an almost catastrophic dive.

An Airbus spokesman insisted there were no similarities between the Qantas and Air France accidents, telling AFP that the latter jet was fitted with an ADIRU from a different manufacturer.

Also in Rio, police began collecting genetic samples from relatives of the passengers on the doomed flight in order to accelerate the identification process should any remains from the crash be found.