Five people were killed and 40 others injured when a bus carrying a Dutch tour group crashed and overturned in a remote Alpine region of eastern Switzerland, authorities said Friday.

The accident occurred late Thursday afternoon on the road between the Alpine villages of Zernez and Susch in the canton of Graubünden. The coach reportedly struck a roadside barrier, left the road and overturned, coming to rest on its side near a section undergoing road maintenance. No other vehicle was reported to have been involved.

The bus was carrying 45 people, all Dutch nationals, according to Swiss police and Dutch emergency assistance officials. The victims were part of a tour organized by Dutch travel company Oad. Earlier reports had put the number of passengers at 48, but police later confirmed that 45 people were aboard.

Of the 40 people injured, three were in serious condition, while seven sustained moderate injuries. The remaining 30 suffered minor injuries, police said.

A large-scale emergency response was launched following the crash, with rescue helicopters and ambulance crews transporting injured passengers to hospitals. Emergency personnel, police and firefighters remained at the scene for hours as authorities worked to recover the victims and secure the area.

The identities of those who died had not yet been released as authorities continued the process of identifying everyone involved.

The exact cause of the crash remains under investigation. Swiss police and the Graubünden public prosecutor's office are examining the circumstances surrounding the accident, including what caused the coach to collide with the roadside barrier.

Swiss President Guy Parmelin said he was “deeply shocked and dismayed” by the tragedy and offered his condolences to the victims' families. He also pledged that Swiss authorities would conduct a comprehensive investigation into the accident.

King Willem-Alexander and Queen Máxima of the Netherlands also expressed their condolences, saying their thoughts were with the bereaved families, those anxiously awaiting news of loved ones and those injured.

Dutch travel officials and Oad, the company that organized the trip, expressed shock over the crash and said they were supporting those affected.

The accident occurred in the Engadine region, a mountainous area near the Swiss National Park that attracts large numbers of visitors. The road between Zernez and Susch was temporarily closed following the crash as rescue and recovery operations continued.

Authorities have not yet indicated when the full investigation will be completed. (ILKHA)