PARIS, Dec 5 (AFP) - French Prime Minister Jean-Pierre Raffarin voiced his concern Sunday at a bungled training exercise by police who allowed a bag with a small amount of explosives to be flown out of the main Paris airport.

The slab, described by security officials as "no more dangerous than a bar of chocolate," was slipped into a hold-all by two dog-handlers.

They chose the bag at random as it passed along a conveyer belt between the check-in desks and aircraft loading bays at Charles de Gaulle airport.

The exercise Friday evening was designed to test the dogs' ability to sniff out drugs.

One successfully detected the item, but the other did not, but before they got another chance, the bag had been whisked off towards its destination.

Police have no idea which of around 80 possible flights the bag was placed on, and have informed all the relevant airlines.

So far there is no news. "The explosives are totally harmless. They cannot react to shock or fire, and there is no detonator," assured an official.

An investigation is underway and the two dog-handlers may face disciplinary procedures, a spokesman said.

In a statement, Raffarin said that while the fight against terrorism was a government priority, he was "concerned" at how the exercise was carried out.

He "insisted such activities should henceforth be carried out according to criteria strictly guaranteeing the privacy of passengers," his office said.

Raffarin also underlined that the procedure was liable to raise the danger that the passenger would be placed under suspicion by foreign authorities when he or she arrived at their destination country.

In the meantime, police say the traveller might not even have noticed their extra baggage.

"It is a small blue case, between 50 and 60 centimetres long," a spokesman said, describing the hold-all. "It is quite possible that the person who owns it has still not found the explosives."