The Mean Girls star is currently serving three months of court-ordered treatment for a probation violation and she was enrolled at California's famous Betty Ford centre until earlier this month (Dec10) when she moved to another facility.
The switch came after an alleged clash with an employee, who was later fired for giving details about the incident to the media.
It has now been revealed that officials at the California Department of Public Health have launched a probe into the Betty Ford clinic, although the agency has not confirmed whether the investigation is linked to Lohan's case.
The Associated Press reports the former employee's interview with website TMZ.com could violate state and federal medical privacy laws.
Lohan's mother Dina has since spoken out about her daughter's stay at Betty Ford, insisting staff at the centre were "fabulous" and "really helped" the actress.