Prosecutors in Panama said Monday they have brought murder charges against a man in the slaying of seven young people whose bodies were found near Lake Gatun, which forms part of the Panama Canal.

Prosecutors did not provide details about the suspect, who was detained Sunday and is the only one arrested so far in the case. Investigators have said there is evidence other people may have been involved.

The rare mass slaying of four men and three women has shocked Panama, in part because the victims were so young, aged 17 to 22.

The victims were part of a group of 13 local youths who set out for a hike last Friday; six escaped and made their way home. Five of the bodies were found Saturday in an abandoned military bunker probably dating from the time of U.S. control of the waterway.

Investigators said the bodies bore signs of bullet wounds. Prosecutor Adolfo Pineda said the survivors had provided information on the killings.