The investigation into one of the worst rail disasters in France is focusing on a loose metal splint.
The train was en route for Limoges in central France when it derailed, skidded and slammed into the station platform in the small town of Brétigny-sur-Orge.
Six of the 385 passengers are dead and 14 remain hospitalised, two are serious. The crash happened at the start of the traditional French summer holiday season.
French Transport Minister Frederic Cuvillier praised the driver who sent out an alert quickly, preventing a pileup.
Sabotage has not been ruled out as a cause of the accident. Three separate inquiries continue.