Investigators in Chateauroux are trying to establish how Birmingham University student Isabel Peake died. It is thought that she fell or was pushed.

They want to find the youths as well as other passengers and possible witnesses who have not yet come forward.

A special unit to investigate her death has been announced at a news conference in the town of Chateauroux in central France, after a visit from the general in charge of police for the Orleans region.

Turbulence ruled out

He announced the setting up of what was called an exclusive and permanent unit, backed by the national police headquarters in Paris.

The 20-year-old's battered and partially-clothed body was found lying by the side of the main Limoges-Paris railway line at the village of Chabenet, near Limoges, on 13 October.

It had been considered possible that the turbulence caused by the train's speed - about 100mph - had ripped off the student's clothes.

But on Wednesday that theory was ruled out.

Tests on Ms Peake's body found no evidence of rape.

Soldiers interviewed

They also confirmed that the train in which she was travelling came from Brives, in the Correze region, and not Toulouse as had previously been thought.

Soldiers on leave from the 126th Infantry Regiment based in Brives were on the train and have been interviewed by officers from Chateauroux.

But police, who have set up a major incident room in Chateauroux, said they were not blaming the soldiers.

"It is a lead like any other," officers said.

Police said they were still "looking at all possibilities" and were trying to trace passengers, including "young delinquents" who often travelled on overnight trains.

Taxi driver sought

Police said they could not yet issue a photofit picture of Ms Peake's suspected attacker or attackers, but some witnesses had come up with "useable" information.

They were also trying to find the taxi driver who took Isabel to Limoges station.

The chief prosecutor in the case, Christian Ponsard, said that about £150 of cash in her bag was found by officers on the track about 10 miles away from where her body was found.

Because the money, her passport and papers were in the bag, robbery has been ruled out as a motive, investigators said.

Ms Peake, a third-year student, was just two weeks into an exchange programme at the University of Limoges as part of her four-year undergraduate degree course.