Trafigura Group, one of the world’s biggest metals traders, was among the companies that received bags of stones from a London Metal Exchange warehouse instead of the nickel briquettes they had paid for.

The amounts of money involved are small, but the issue presents a fresh headache as the company wades through the fallout of a massive alleged fraud it reported last month — also involving missing nickel. Trafigura has said there’s no connection between the bags of stones discovered on the LME and its legal action against Indian businessman Prateek Gupta, who it accuses of perpetrating a vast and “systematic” fraud.

Trafigura was one of several companies that in recent months bought cargoes purporting to be nickel that had been held on the LME at a warehouse in Rotterdam run by Access World, the people said. Trafigura’s material was shipped to New Orleans, where the problems were discovered after the bags were found to have the wrong weight.

Trafigura and the LME declined to comment.

Other shipments were made to nickel trader Stratton Metals in Europe, some of the people said, asking not to be named as the matter isn’t public.

After the LME was alerted about issues with some shipments, the exchange oversaw an inspection of all the nickel held at the Rotterdam facility. It found that bags of material backing nine LME contracts, equivalent to 54 tons, contained stones rather than nickel. Bloomberg reported on Monday that JPMorgan Chase & Co. was the owner of those nine contracts, which have been canceled by the LME.

The amount of problem material that had been delivered out of the Access World warehouse was similarly small, at just a few tons. Stratton, for example, received 12 tons, according to one of the people.

But the discovery of another issue in Trafigura’s nickel book is a blow to its beleaguered metals traders, coming after the revelation that the company recorded a $577-million impairment as a result of a massive alleged fraud against it. That issue was also discovered when Trafigura opened cargoes it had bought only to discover that they contained low-value materials like carbon steel rather than nickel.

Trafigura previously said that it was not the owner of the nine nickel contracts invalidated by the LME, and that the issues identified by the LME had no connection with its fraud case.

Access World said on Monday it believes the issue is “an isolated case and specific to one warehouse in Rotterdam.”