Friday’s derailment may have been caused by a connecting bar that had come loose at a rail switchpoint at Bretigny-sur-Orge station, about 25 kilometers south of Paris, said rail operator Société Nationale des Chemins de fer Français (SNCF).
The joint bar “broke away, it became detached and came out of its housing,” said Pierre Izard, the SNCF’s general manager for infrastructure.
It “lodged itself at the center of the switch, prevented the normal progression of the train’s wheels and seems to have caused the train’s derailment,” he said.
The switch had been checked on July 4 and another train had passed over it half an hour before the accident, said the company.
The SNCF has ordered immediate checks of some 5,000 similar joints on its network.
Transport Minister Frederic Cuvillier said human error was not to blame for the accident.
He praised the train’s driver who he said “had absolutely extraordinary reflexes by sending the alert immediately,” preventing a collision with an incoming train.
But France’s regional rail lines were out of date after the SNCF focused much of its attention in recent years on high-speed TGV lines, Cuvillier said.
“We cannot be satisfied with rolling stock that is 30 years old,” he added. “The situation is severe, with the deterioration in recent years of traditional lines because of a lack of resources.”
A railway passenger association also denounced what it called “rust-bucket trains” and the practice of coupling different types of trains together. It called for proper inspections.