Human error has been ruled out by France’s transport minister and the focus of the investigation is on a detached piece of metal in a switching joint on the tracks. The national rail company, SNCF, has already taken blame for Friday evening’s crash at Bretigny-Sur-Orge station, which occurred at the start of a busy holiday weekend.

“The SNCF considers itself responsible,” rail company chief Guillaume Pepy said. “It is responsible for the lives of its clients.”

The packed train, carrying around 385 passengers, was traveling below the speed limit at 85 mph when it derailed, skidded and slammed into the station platform in the small town outside the capital. It was 20 minutes into a scheduled three-hour trip to Limoges in central France.

The 700-ton crane, sent from northern France, towered over small buildings that surround the railway station to begin work on clearing the tracks.

The operation is an “extraordinarily difficult technique given that we are in a train station,” Pepy said. “For the moment, we don’t know how long it could take.” He said the operation could last through Sunday, which is the July 14 Bastille Day holiday, and into Monday.

Pepy stressed the crane operators will be careful and slow in lifting the cars, because authorities need to verify that nobody is trapped underneath the wreckage. He said investigators found that a 22-pound piece of metal he compared to a staple between two rails in a switching system, which guides trains from one track to another, seems to have “detached itself from the rails, lifted and constituted the initial cause of the derailment.”

Investigators were looking into how this happened since another train had traveled safely through the station about 30 minutes before. In addition, they were trying to determine why the train’s third car was the first to derail.

Pierre Izard, another SNCF official, said the metal piece “moved into the center of the switch and in this position it prevented the normal passage of the train’s wheels and it may have caused the derailment.”

But Pepy said track failure was a likely preliminary cause. “There can be no (definitive) answer in a few minutes, in a few days,” he said at a news conference.

The train was about 12 miles into its 250-mile journey to Limoges.

Passengers and officials in train stations throughout France held a minute of silence at noon to commemorate the accident. Hundreds of thousands of people were expected to take trains this weekend to the coast, mountains and to see family. Summer weekends are always busy on France’s extensive rail network, but this one is typically one of the busiest because of Bastille Day.

The governor of the Essonne region, Michel Fuzeau, gave the latest casualty figures, saying that in addition to the dead, 22 people remained hospitalized, two of them in a life-threatening state. Nearly 200 people had initially been treated for injuries, either at the scene or at hospitals.

While the death toll has not budged since hours after the crash, Fuzeau, the regional prefect or governor, said that until an overturned train car is lifted, it was impossible to know if there could be more people trapped under it.

“This is only a hypothesis and we hope it’s not (the case),” he told reporters.

The crash was the country’s deadliest in years, but Transport Minister Frederic Cuvillier said it could have been worse and praised the driver who sent out an alert quickly, preventing a pileup. Cuvillier acknowledged that there was some criticism that France hasn’t invested enough in maintaining infrastructure.

“But for the moment we have no information that allows us to confirm that the dilapidation of the network was the cause of this derailment,” he said on French television.

Keira Ichti, who lives in the town where the train crashed, said she was terrified when she found out about the accident because her daughter works at the station. It was “total panic. My heart was beating so fast. I had no strength,” the 56-year-old said.

She later found her daughter outside the station.