A 34-year-old American man died Thursday in a wingsuit jumping accident in the Swiss mountains, local police said. The cause of the fatal crash is unknown.

The accident happened in the Churfirsten mountains, a group of seven limestone peaks in the St Gallen region of northeast Switzerland that are popular with hikers, mountain bikers and para-gliders.

St Gallen police said in a statement that the man "jumped with his wingsuit from the Sputnik jump on the Hinterrugg" -- at 2,306 metres (7,566 feet) the highest peak in the group and a well-known spot for BASE jumping.

"For reasons that are still unclear, he crashed on the flight route towards Walenstadt," the small town below.

The man, who was not named by police, was found dead by an air rescue crew.

Police said they were now investigating the cause of the crash.