SHARM EL-SHEIKH, Egypt - France said on Monday it attached little credence to a previously unknown Islamic group's claim to have brought down a plane that crashed off Egypt, killing 133 French tourists and 15 other people.

Egypt again defended the safety record of Flash Airlines, operators of the Boeing 737 that plunged into the Red Sea on Saturday, but Switzerland issued a fresh statement that it had banned the Egyptian company from its airspace on safety grounds.

French civil aviation authority head Michel Wachenheim said France's own checks on the doomed plane had showed "nothing abnormal".

An anonymous caller claiming to represent a Yemen-based group called Ansar al-Haq (Followers of the Truth) told an international news agency the group had downed the plane and would also attack Air France planes unless the French government dropped plans to ban Islamic headscarves from state schools.

Although France says no conclusions can be made on why the plane crashed until all the facts are known, French Justice Minister Dominique Perben said: "On the basis of the information in my possession, (the claim) is not very credible."

The Egyptian Government has ruled out an attack on the charter plane, which crashed shortly after take-off from the Red Sea resort of Sharm el-Sheikh bound for Cairo and Paris.

Key recorders

French officials said the plane's two flight recorders, which could hold the key to explaining why it crashed, had not been located yet. The so-called "black boxes" record technical data about the flight and conversations between the pilots.

French experts had to delay plans to use a submersible robot to search for the flight recorders from the wreckage of the plane, now lying in deep water off Sharm el-Sheikh.

"The robot arrived yesterday ... but it takes time to prepare the specialist equipment and coordinate and organize with the teams," said France's ambassador to Egypt, Jean-Claude Cousseran.

Rescue teams have found body parts and wreckage but no survivors.

Swiss authorities said on Monday they had found two Flash aircraft unsafe in 2002, raising the possibility that one was the plane that crashed on Saturday.

In Cairo, Flash officials were not immediately available for comment on the Swiss statement.

But they have said the doomed plane was one of only two that Flash has operated in recent years, including all of 2002, although Swiss officials were unable to confirm positively that it was one of those they had inspected.

Switzerland said it had inspected one of Flash's aircraft in April 2002 and found various problems, including missing navigation documents, fuel reserves not calculated to international standards and maintenance deficiencies.

The Swiss Federal Office for Civil Aviation said an inspection of a second Flash aircraft in October 2002 had revealed "essentially the same defects".

After Flash failed to provide sufficient proof the defects had been remedied, it was barred from landing in Switzerland a few days later, the office said.

Egyptian Civil Aviation Minister Ahmed Mohamed Shafiq Zaki said earlier on Monday the Swiss had let a Flash plane take off from Zurich with 148 Swiss tourists in October 2002 after giving the plane a safety check.

"That means it was 100 per cent safe," he said.

(Agencies via Xinhua)