Gold bars stamped with fake logos of major refineries have been circulated into the global market and landed in the vaults of JPMorgan Chase & Co. — part of a plot to launder smuggled or illegal specimens of the precious metal, according to a report.

Bars worth at least $50 million stamped with the logos of Swiss refineries that did not produce them have been identified by all four of the country’s top gold refiners in the last three years, Reuters reported.

They have been found in the vaults of JPMorgan, one of the major banks at the center of the market in bullion, senior executives at gold refineries, banks and other industry sources told the news outlet.

Four executives told Reuters that at least 1,000 of the bars have been found — a small share of output from the gold industry, which produces about 2 million to 2.5 million such bars every year.

But the forgeries are sophisticated, so thousands of additional ones may have gone undetected, according to the head of Switzerland’s largest refinery.

“The latest fake bars … are highly professionally done,” Michael Mesaric, chief executive of refinery Valcambi, told Reuters, adding that there are “way, way, way more still in circulation.”

Blocks of cheaper metal plated with gold are relatively common in the industry and are often easy to detect, but the forgeries in these cases are more subtle — the high-purity gold is real, with only the markings faked.

Fake-branded gold is a relatively new way to flout global measures to block conflict minerals and prevent money-laundering. The forgeries pose a problem for global refiners, financiers and regulators as they try to rid the world of illegal trade in bullion.

Without a stamp from a prestigious refinery, such gold would be forced into underground channels, or priced at a discount.

But by pirating major brands, metal that has been mined or processed in locations that would not otherwise be legal or acceptable in the West — such as parts of Africa, Venezuela or North Korea — can be slipped into the market, channeling funds to criminals or sanctioned regimes.

It was unclear who is producing the bars found so far, but executives and bankers told Reuters they believed most originate in China, the world’s largest gold producer and importer, and have infiltrated the market through trading houses in Hong Kong, Japan and Thailand.

Once accepted by a mainstream dealer, they can quickly slip into the global supply chains.

In 2017, JPMorgan, one of five banks that finalize trades in the $10 trillion-a-year London gold market, found that its vaults contained at least two gold bars stamped with the same ID number, 10 people familiar with the matter told Reuters.

The news outlet couldn’t determine exactly where the vaults were.

JP Morgan declined to directly address questions about the fake bullion.

“It’s our standard practice to immediately alert the appropriate authorities and refineries should we discover mismarked gold kilobars during routine checks and procedures,” the bank said in a statement.

“Fortunately, we have yet to have an incident resulting in a loss to the firm or a client,” it added.

Kilobars are small — about the size and thickness of a cellphone — unlike the roughly 12.5-kilo bars typically stored in the world’s central banks.

The identifying features stamped onto a bar’s surface include the logo of the refinery that produced it, its purity, weight and a unique ID number. Each one is worth around $50,000 at current prices.

The Shanghai Gold Exchange, which regulates China’s gold market, said it was unaware of counterfeit bars being made in or transported through the country.

“The Shanghai Gold Exchange has established a thorough delivery and storage system. The process for gold (material) to enter the warehouse is strictly managed and in compliance with the regulations,” it said in a statement.

When forged bars were found, they were returned to the refiner concerned. Those returned to Switzerland have been reported by refiners to authorities who impounded them, according to the report.

Swiss customs officials said 655 forged bars were reported in 2017 and 2018 to authorities in Ticino, a region bordering Italy that contains three of Switzerland’s four large refineries.

“In all cases the marking of the 1 kg bars were fake,” a customs official told Reuters in an email, without commenting further.