The tide is high, and so are the locals.

Beach-combers are well accustomed to picking up interesting-looking shells, spotting a pretty dogfish egg-sac or finding an old boot.

But when packages of cocaine started washing up on the shores of southwest France, the local police swiftly took over the search.

Nearly 900kg of the narcotic has so far washed up on the Atlantic coast since mid-October – and that’s just what the authorities know about.

Officials say the cocaine – the street version of which the UN says retails at around $70 for a single gram in France – is extremely pure at 83 percent, and warned people who find the packages not to touch them but to inform the police.

That, surprisingly, has not stopped everyone.

On Monday, a 17-year-old was caught with five kilos of cocaine at Lacanau, a closed-off surfing beach near the southwestern city of Bordeaux. He had come from Toulouse, a three-hour drive away.

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Nearly half a dozen other beaches in the area have been closed as well, with police stopping walkers for searches and also checking cars leaving nearby parking lots.

‘Tempting’

A police helicopter was also being used along the 125-km (78-mile) stretch between Cap Ferret and Soulac-sur-Mer, which includes the Lacanau beach.

A woman who gave her name as Martine failed to notice the closure signs at the Porge beach on Monday, when officers told her and a friend to leave.

“When we turned around, we saw a package next to the water,” she said, saying they alerted the police, who estimated it weighed some four kilograms before sealing it in a plastic bag.

“It would have been tempting to take it, but we’re honest,” she told the AFP news agency.

“We’ve recovered 872 kilos,” Philippe Astruc, the prosecutor in the western city of Rennes, where officials are coordinating the searches, told the AFP in a statement.

It was a sharp jump from just two days ago, when 763kg had been reported.

‘Dangerous’

“Intense surveillance has been set up by different services, notably the customs agency, all along the French coast,” Astruc’s office said.

“In this form, it is a very dangerous product that could cause an overdose,” it said.

Officials have reported the drugs turning up on beaches near Nantes all the way to the resort town of Biarritz, more than 500km (300 miles) to the south, where the leaders of the world’s most powerful nations met for a summit in August.

French investigators are working with European counterparts, as well as the US Drug Enforcement Agency to try to determine why the drugs are washing up.

“There are several hypotheses, but for the moment we think it’s likely they were jettisoned because of a mechanical problem or during a storm,” Astruc said in a statement.

The Sud-Ouest newspaper reported over the weekend that some packages found on the beach at Arcachon, southwest of Bordeaux, were marked “Diamante” or “Brillante”.

Packages of cocaine marked with the same words also reportedly washed up in Florida during Hurricane Dorian in September, it said.

Police seized a record of more than 140 tonnes of cocaine across Europe in 2017, according to the most recent data available from the EU’s European Monitoring Centre for Drugs and Drug Addiction, published in June.

Most were seized in Belgium and Spain, long the main port of entry for the drug, and its purity has increased markedly over the past 10 years, the agency said.