(CNN) -- A fatal train derailment south of Paris was caused by a part disconnecting from the switching mechanism on the tracks, the head of the French national railway company said Saturday.
Six people were killed and 22 others injured late Friday afternoon when four cars of the train, a regional service bound for the city of Limoges, went off the track at Bretigny-sur-Orge station.
On Saturday night, officials said the death toll was definitive.
"We are now sure that there are no additional victims," said Michel Fuzeau, the prefect for the Essonne department. A train car that was lying on its side at the station was lifted up and then inspected by firefighters and police, who did not find any additional victims, Fuzeau said.
At least six dead in French train wreck
Passenger describes France train wreck
Many casualties in French train wreck Various government officials and authorities had earlier given conflicting death tolls.
A moment's silence for the victims was to be observed at noon Saturday at rail stations and on trains across France, said Guillaume Pepy, president of the railway company SNCF.
Services have been suspended on the line where the accident occurred, Pepy said.
Footage from the station Friday showed a scene of devastation, with the derailed train cars twisted and crumpled across the platform and track. Rescue workers searched the wreckage for the dead and injured.
French President Francois Hollande visited the scene of the derailment Friday, when he praised the work of emergency responders.
Hollande, who said he'd traveled on the route before, announced three investigations: a judicial inquiry, an internal inquiry within SNCF and an inquiry that will be handled by the country's transport ministry.
The train was carrying about 370 people at the time of the incident.
Alain Krakovitch, responsible for rail service safety and quality at SNCF, told BFMTV that the train was traveling at a normal speed when it reached Bretigny-sur-Orge about 20 minutes after its departure from Paris Austerlitz.
The train and station platform were busy with travelers on what is a holiday weekend in France.
A passenger in the first car of the train, whose name was given only as Laurent, told BFMTV he had felt a powerful shaking, lasting 10 to 15 seconds. Smoke was everywhere, he said.
His rail car remained on the track, but the passengers could see the derailed cars behind, he said.
Officials praised the swift reaction of the train's driver, which meant other train services were halted before they could hit the wreckage.
"The train driver had an extraordinary reflex in immediately signaling the alert," Transport Minister Frederic Cuvillier told BFMTV.