Source: p 231 of 296, Understanding Housing Policy, by Brian Lund
[1.] ... In addition, the CRE [Commission for Racial Equality] acquired the power to instigate a formal investigation into an organisation of which it had a reasonable belief that discriminatory procedures were being practised. ...
Is the preposition of correct? I would've guessed IN, because this is how I parse the sentence:
[2.] ... the CRE acquired the power to instigate a formal investigation into an organisation IN which ... discriminatory procedures were being practised. ...