As many as 50 women have described harrowing tales of abuse they allegedly suffered while students at a Sydney girls' college, one claiming she was raped in the school's sandstone dungeon.

Detectives have formed Strike Force Bilvo to investigate the new claims against two of three former officials at the Parramatta Girls Training School who are still alive, the Daily Telegraph reports.

"Strike Force Bilvo was created to investigate the complaints and the former staff members named at the royal commission hearings are now at the centre of the investigation," Acting Superintendent Robert Toynton told the newspaper.

"The investigation is focused on two living alleged offenders."

The two persons of interest were identified in the child sex abuse royal commission as Frank Valentine, 75, who now lives in Brisbane's northeast, and Noel Greenaway, who resides in the Sydney suburb of Normanhurst.

Last year the royal commission heard the allegations of almost 50 former residents of the school who claimed to be sexually abused as children between 1950 and 1974.

One woman claimed Mr Valentine forced her to have sex in a dungeon beneath the school.

The existence of the convict-built bunker with walls half a metre thick was confirmed by witnesses.

Thousands of pages of evidence have been seized by the strike force across 44 separate search warrants.

Almost 50 women have come forward with claims of sex abuse at the hands of three former school officials. (Supplied)

One woman claimed she was forced to have sex in the school's convict-built bunker, which has walls half a metre thick. (Supplied)