Five people have died and 40 others have been injured after a tour coach carrying Dutch holidaymakers overturned in the south-eastern Swiss Alps, cantonal police confirmed on Friday.

Graubünden cantonal police said three people sustained serious injuries and that all 40 survivors were transported to hospitals across the region. While earlier reports indicated that 48 passengers were on board, police have now confirmed there were 45 occupants in total. The victims have not yet been formally identified.

The vehicle struck a safety barrier in a roadworks area before leaving the carriageway and overturning on an embankment between the villages of Susch and Zernez in the Engadine valley, near the Swiss National Park.

A major rescue operation involved seven helicopters from Switzerland and Austria, local fire departments, and the Plaiv road rescue service. Graubünden's public prosecutor's office and police have opened an official investigation into the cause of the crash, and the mountain road remains closed.

Netherlands-based tour operator Oad, which organised the trip, said it was "deeply shocked and devastated by the tragic accident" and is assisting the emergency response. The passengers had left the Netherlands on Monday and were on a day excursion to Switzerland from Austria when the crash occurred.

Dutch Prime Minister Rob Jetten, King Willem-Alexander, and Queen Máxima expressed their condolences to those affected, joining Swiss President Guy Parmelin in offering sympathies to the families. I will continue to monitor the investigation and update this report as further information is released.