NAPLES, Italy, March 26 (UPI) -- Italian police freed two teenage Bulgarian girls from a circus where they were forced to swim in a tank of piranhas and allow snakes to crawl over them.

The owner of the Marino Circus, his son and his son-in-law were arrested and charged with holding the Bulgarian girls in slavery and breaching international human rights conventions, The Times of London reported Wednesday.

Police were tipped off to the circus south of Naples by a spectator who reportedly saw the elder sister, Guisi,19, trying to escape from the piranha tank while circus owner Enrico Raffaele Ingrassia, 57, allegedly held her down.

Her sister, Olga, 16, was allegedly forced to perform by allowing snakes to crawl over her body and bite her.

Ingrassia's daughter, who wasn't charged, told police that the Bulgarian girls and their parents had been held as slaves since January. They were allegedly forbidden to leave the camp and forced to work 15- and 20-hour shifts, the BBC reported.