Former FBI agent Ted Gunderson detailed his investigation...

Former FBI agent Ted Gunderson detailed his investigation into alleged underground tunnels beneath the McMartin Preschool in Los Angeles, California.

Children alleged they were subjected to horrific abuse in various locations, including secret rooms accessed through tunnels or even by being flushed down toilets.

Victims claimed these hidden chambers hosted dark rituals where men and women, cloaked in hooded black robes, inflicted abuse.

The accusations also included accounts of animals being mutilated in front of children to instill fear and enforce silence.

The preschool building was demolished in 1990 and the site has since been redeveloped.