Investigators were seeking to determine the reason for the accident. The head of the SNCF rail authority called it a "catastrophe."
Interior Minister Manuel Valls said at least seven people are believed dead and several dozen injured, but added that the casualty toll is "in constant evolution."
Officials did not comment on reports that some passengers may still be trapped on the train.
The SNCF said the train was carrying some 385 passengers when it derailed Friday evening at 5:15 p.m. (1515 GMT) and crashed into the station at Bretigny-sur-Orge, some 20 kilometers (12 miles) south of Paris. The train was headed from Paris to Limoges.
A passenger speaking on France's BFM television said the train was going at a normal speed and was not meant to stop at Bretigny-sur-Orge. He described children unattended in the chaotic aftermath. He said there are swarms of emergency workers at the scene.
Two train cars, cars number 3 and 4, initially derailed, then knocked the other cars off the track, SNCF chief Guillaume Pepy said. "Some cars simply derailed, others are leaning, others fell over," he said.
All trains from Paris' Gare d'Austerlitz were suspended after the accident.