Twelve people were taken to the hospital on Tuesday evening after suffering from the effects of carbon monoxide poisoning at a hotel on Scheveningen’s pier.

The emergency services were alerted shortly before 10 pm after a number of people, both guests and staff, reported feeling sick and dizzy. Two ambulance workers were among those taken to the hospital.

The De Pier Suites hotel was then evacuated for a time before guests were allowed to return.

As yet, it is unclear what caused the carbon monoxide leak, and the hotel declined to answer questions from news agency ANP.

Every year, 10 to 15 people in the Netherlands die from carbon monoxide poisoning.