Swiss food giant Nestle said on Thursday that its offices in France were being searched by French authorities, confirming earlier reports.
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.
The search was being carried out by the Directorate General for Competition Policy, Consumer Affairs and Fraud Control (DGCCRF), according to Radio France.
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 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.
Nestle has been under pressure for some time over Perrier and other brands as EU regulations strictly limit what treatments are allowed for any product marketed as natural mineral water.
In May, French authorities ordered Nestle to stop filtering its Perrier and held back on allowing the under-pressure brand from using the description 'natural mineral water'.
Last month, Nestle Waters has been fined more than £454,000 by Swiss authorities for having used activated carbon filters on its Henniez bottled mineral water.
In 2024, Nestle Waters admitted using banned filters and ultra-violet treatment on mineral waters, which must be processed naturally by law.