Twenty-eight Belgians were killed in a serious bus accident that occurred in southwest Switzerland on Tuesday night, Swiss police confirmed early Wednesday, according to Xinhua.

The death victims included 22 children. Twenty-four other Belgians were injured in the incident, said the police, adding that all the 52 were on the bus when the tragedy occurred.

All the passengers on that bus were tourists of Belgian nationality. The tragedy took place on their way back home.

The accident happened around 9:15 p.m. local time (2015 GMT) in a tunnel near Sierre in the Swiss canton of Valais. Local police said the bus apparently struck the left side of the tunnel, veered right and crashed into an emergency lane inside the tunnel.

Large-scale rescue efforts were reported to be present on site, ambulances and helicopters were moving in and out, transporting the injured for treatment.

Local police also set up a telephone hotline connecting Belgium and Switzerland for families of the victims.