A mistake by Luxembourg's state rail company caused last week's train crash in northeast France, a minister said.
The two trains were travelling on the same track when they hit
Six people died when a passenger train and a goods train collided head-on near the Luxembourg border on 11 October.
An initial probe showed that signallers in Luxembourg sent the passenger train onto the same track as the goods train, Transport Minister Lucien Lux said.
"We have to admit that the main responsibility probably lies with Luxembourg," he told a news conference.
"It's tough to say, but it's the fault of the CFL (state rail company Chemins de Fer Luxembourgeois)."
French Transport Minister Dominique Perben praised "very good co-operation" between the two nations' rail companies in the investigation.
Sixteen people were also injured in the crash, two of them seriously.