Swiss food giant Nestle has confirmed its offices in France were being searched by local authorities.
Nestle has been under investigation by a Paris judicial court since February for using unauthorised filters in the production of its bottled mineral waters.
"We continue to cooperate fully with the authorities as we have always done," a spokesperson said on Thursday after reports emerged.
The search was being carried out by the Directorate General for Competition Policy, Consumer Affairs and Fraud Control (DGCCRF), according to Radio France.
The agency did not immediately respond to a request for comment.
The probe was triggered by allegations by non-profit Foodwatch that Nestle Waters was using illegal filtration systems for its water to mask contamination by bacteria and pesticides.
Nestle Waters produces the Perrier and Contrex brands.
Nestle Waters France said in February that microfiltration had been used for years in the industry to ensure the safety of natural mineral waters while preserving their mineral composition.
