The cause of the damage in the Gotthard road tunnel has been identified as "stress redistribution in the local mountains", which led to pressure changes and then to a crack in the intermediate ceiling, the Federal Roads Office (FRO) announced this on Wednesday.
Such stress shifts in the mountains could put a lot of strain on structures - such as tunnels, according to a statement. As a result, similar damage occurred in the Gotthard road tunnel in 1985.
There are several possibilities why these rearrangements could occur: movements in the mountain, construction work or even tectonic influences. FRO is therefore in contact with the Swiss Seismological Service, which recorded a “seismic signal” on Sunday afternoon at 4:10 p.m.
It is currently being clarified whether this signal is related to the events in the tunnel.
In any case, FRO could rule out structural conditions of the tunnel as the cause of the damage, it said. Construction work is on track and FRO expects to be able to open the tunnel to traffic this week.