France's president is calling for an investigation into the death of a protester during a demonstration against a dam project in southwest France.

Speaking to reporters Tuesday, President Francois Hollande called for "the full truth of what happened during this violent demonstration and the cause of death" to be revealed.

The body of 21-year-old Remi Fraisse was discovered early Sunday after a protest in which several hundred demonstrators clashed with police near Lisle-sur-Tarn, 670 kilometers (420 miles) south of Paris. An autopsy found that a large wound on Fraisse's back was caused by some kind of explosion, but investigators haven't concluded who or what caused it.

The death has sparked days of protests by opponents of the dam project. The government has accused them of "politicizing" the tragedy.