Officials in northern France are investigating whether the derailment of a passenger train on Friday evening was the result of a malicious act.

“At this stage, the leading theory is that a piece of rail was present on one of the tracks, potentially causing the derailment. The reason for its presence is unknown,” prosecutor Sébastien Gallois said on Saturday.

Local media say 186 passengers were on board the train that was operating between Rouen and Caen in Normandy.

Forty-four people were treated for injuries, including an 18-year-old woman who was airlifted to hospital in a critical condition.

“The train’s ‘black box’ has been seized. Several interviews are scheduled, and a court-appointed expert has been called in,” prosecutor Gallois said in a press release.

“The main victim is still in hospital but her life is no longer in danger. The other victims have received care and treatment; they have either been discharged or are about to be.”

The Rouen prosecutor’s office earlier said the train driver had tested negative for drugs and alcohol.

The train derailed near Cléon, just south of Rouen, shortly before 20:00 (18:00 GMT), and some 140 firefighters and other emergency teams were immediately deployed to the crash scene.

“Suddenly there were a few jolts, and then after about three seconds it got stronger and stronger,” Louis, a passenger on the train, told ICI Normandie radio.

“I couldn’t stay in my seat anymore. The windows partially shattered, the stones from the track came into the carriage. It was really shocking. I’m still shaking,” he added.