It seemed like a worthwhile experiment to a small winery: Submerge bottles of wine in sea water to see how they age.

But a federal agency is concerned that ocean water could contaminate the wine.

For two years, Napa Valley, California-based Mira Winery has been submerging bottles of wine in the harbour in Charleston, South Carolina, where its president lives, to determine the effects of water, motion, light and temperature on ageing.

But last week the federal Alcohol and Tobacco Tax and Trade Bureau issued an advisory saying water pressure could cause contaminants to seep into the bottles. It said the bureau will issue no labels for ocean-aged products until the Food and Drug Administration determines they are unadulterated.

Mira produces several thousands of cases a wine a year but only 20 have been submerged, company president Jim “Bear” Dyke jnr said Monday. The eight cases in the harbour now will be retrieved in May.