Swiss rail operator SBB said that repairing the world’s longest rail tunnel will take much longer than anticipated and it won’t be fully open for passenger and freight trains for almost another year.

The Gotthard base tunnel, an important north-south link for Switzerland and Europe, was damaged when a freight train derailed on Aug. 10. 

The scale of the damage has proved much more serious than initially assumed and full operations in both tubes may not be possible until September 2024, SBB said Thursday. It added that the cost to reopen the tunnel will amount to 100-130 million Swiss francs ($111-144 million). 

SBB is trying to speed up the work, which involves replacing rails, concrete, high-speed switches and more than 20,000 sleeper blocks.

In the meantime, the company plans to increase capacity for freight traffic during the week, and for passenger traffic at weekends in a timetable change from Dec. 10.