Beaches in southwest France along the Atlantic coast have been shut down after bricks of cocaine and other drugs continue to wash ashore, for weeks now, leaving investigators puzzled over where the illicit substances came from, a prosecutor said Tuesday.

The packages of drugs have turned up daily on beaches as far as 300 miles apart, from Nantes in western France to the resort town of Biarritz near the Spanish border to the south, Philippe Astruc, the prosecutor in the western city of Rennes said.