The Interior Ministry said no link had been established between the bomb and the two recent explosions in Paris which killed seven people and injured more than 100. But it did not say that such a link had been excluded.
The device was spotted by the driver of a Lyons-Nantes express on Saturday morning, and all traffic on the route was stopped while the bomb was defused and the line checked. A fault in the triggering mechanism was said to have prevented it from exploding.
As many as 15 trains were said to have passed the place where the bomb was planted, close to one of the biggest junctions in the TGV network, before it was seen. The device also was not detected by the inspection train that checks the track at the start of each day. From yesterday, the inspection trains were to be double-manned, with a crew member detailed to watch specifically for obstacles.
Officials in the region introduced additional security measures, announcing both mobile and fixed patrols along rail lines, air surveillance, and other measures left undisclosed.
The possibility of an attack on a TGV has been at the back of the French authorities' minds for some time. After the second recent Paris bombing, close to the Arc de Triomphe on 17 August, new security measures were introduced at all main railway stations. Now, only those with tickets for the train which is about to depart are allowed on to platforms, and their luggage is checked. Left-luggage lockers and litter bins at railway stations were closed after the first bomb, at Saint-Michel station on 25 July.
While the Algerian Armed Islamic Group (GIA), which is widely held responsible for the other attacks, is bound to be a favourite suspect for the TGV bomb, there is always the possibility of bombings by other groups which are hostile to the French government. These would include the Corsican and Basque separatists, and anti-nuclear protesters.
n The official opening of the Planet Hollywood restaurant next Sunday has been indefinitely postponed at the request of the Paris police chief because of security worries. Dozens of American film stars were to have attended a party in the Champs-Elysees.