everything I'm reading about the OIG states this is essentially what they are there for.
"The OIG's investigative jurisdiction includes all allegations of criminal wrongdoing or administrative misconduct by DOJ employees, except for allegations of misconduct that "relate to the exercise of the authority of an attorney to investigate litigate, or provide legal advice," which are referred to the DOJ Office of Professional Responsibility (OPR) unless the allegation concerns attorneys who work for OPR.[2]"
https://en.wikipedia.org/wiki/United_States_Department_of_Justice_Office_of_the_Inspector_General