French investigators into Friday’s train crash near Paris are suggesting that a defective points system caused the accident.
At a news conference railway managers from the state railway company SNCF said a metal bar linking the rails to the points had come loose.
The French Transport Minister Frédéric Cuvillier said emergency workers had found no new victims overnight, but more bad news could not be ruled out as teams tried to search overturned carriages.
He praised the train driver, whose immediate reaction in sounding the alarm he said had prevented another train from crashing into the wreckage.
At railway stations across France a minute’s silence has been held for the victims at Brétigny-sur-Orge, 25 kilometres south of Paris.
Six people are known to have died and dozens are seriously injured, with the condition of nine described as “absolutely urgent”.
The minister said the train heading for Limoges in central France was travelling at 137 kilometres an hour when its rear carriages derailed shortly after 5pm CET on Friday.
A passengers’ association has condemned what it called dilapidated railway equipment.