A train derailment that killed seven people and injured around 30 in central France last year was due to a maintenance problem that revealed an 'unprecedented state of decay', according to an experts' report to be made public on Monday, Le Figaro newspaper reported on its website.
If confirmed, the report will deal a new blow to French rail operator SNCF, already hit this year by strikes and a botched order of rolling stock. It declined to comment on the Le Figaro story.
SNCF said last year the derailment had been caused by a steel plate that should have remained bolted to the track but broke off and blocked the path of the train.
Le Figaro said the investigators would say that accident was not caused by a "malicious act", but by a process lasting several months in which the plate had gradually worked itself loose.
Experts had found more than 200 irregularities, of varying degrees of seriousness, in the section of track in question, it said.
"Most of the anomalies were known by the SNCF or its agents and yet they did not remedy them in an adequate fashion," Le Figaro quoted the expert report as saying.
It said the report, which described "an unprecedented state of decay", was not subject to appeal.
The Paris-Limoges train, on a regional service that travels more slowly than France's TGV express trains, derailed at the station of Bretigny-sur-Orge, 26 km (16 miles) south of the capital in July last year. It was carrying 385 people.
This year, the SNCF has faced numerous strikes in protest against a proposed reform of the railway structure, and was embarrassed by a costly mistaken order of hundreds of trains too wide to enter stations.