At least 30 people were pronounced dead Saturday after a stampede in northern Haiti.

Authorities said the death toll could rise, according to Reuters. 

Jean Henri Petit, head of Civil Protection for Haiti’s Nord Department, said the incident took place at the Citadelle Laferrière, an early 19th-century fortress constructed soon after the country gained independence from France.

One of Haiti’s most popular tourist sites, the fortress was filled with students and visitors who had gathered for an annual celebration marking its status as a UNESCO World Heritage site, Petit said.

Prime Minister Alix Didier Fils-Aimé said in a statement that he “extends his sincere condolences to the bereaved families and assures them of his profound solidarity during this time of mourning and great suffering.”