ANAHEIM, Calif. (AP) — Authorities in Anaheim, Calif., have not explained how two parolees who are registered sex offenders could allegedly rape and kill at least four women while wearing GPS trackers.

Police say Franc Cano and Steven Dean Gordon were both wearing ankle bracelets when the women were attacked last fall.

Police say the two men were complying with their required monthly check-ins with authorities, and there was no reason to watch them more closely.

Police say there may be more victims.