A hotline was set up for families and employees of Kronospan, a wood panel factory in Menznau, police said, adding that the perimeter around the plant was sealed off.

Police said the emergency services were on the scene and the area had been largely cordoned off, but gave no further details, saying only they would give further updates later in the day.

Swiss news agency SDA quoted the rescue helicopter service REGA as saying it had flown four seriously injured people to hospital.

Last month, a gunman killed three women and wounded two men in the Swiss village of Daillon, stirring a debate about Switzerland’s fire arms laws that allow its male citizens to retain guns after their mandatory military service.

Gun ownership is widespread in Switzerland, where citizens are allowed to keep their weapons at home outside periods of mandatory military service.

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