The WA Opposition has criticised Police Minister Michelle Roberts for failing to confirm to parliament whether police know the whereabouts of 58 people charged with child sex offences during a major police operation.

Operation Fledermaus has been running since 2016 in the state's North West and has uncovered hundreds of allegations of sex crimes against at least 50 children.

Many of the victims and their alleged abusers live in Roebourne, about 40km from Karratha in WA's Pilbara region.

The opposition had asked the government to reassure the public that police knew the whereabouts of all 58 accused or whether any were listed on the state's sex offender register.