ZURICH (Reuters) -Switzerland imported 284 kg of gold worth around $16 million from Russia in June, customs data showed on Tuesday, down from more than 3 tonnes worth some $200 million in May.

The shipments have raised questions about whether Swiss firms may be helping finance Moscow’s invasion of Ukraine — something Switzerland’s major refineries deny.

Russia is the world’s second-biggest gold producer and Switzerland is the biggest refining hub.

The Swiss government said last month that Russian gold imported in May originated in Russia but was shipped from Britain. They said customs officials were investigating whether the imports had violated any sanctions.

Britain is a gold vaulting and trading centre and stores hundreds of tonnes of gold produced in Russia before it invaded Ukraine.

It is not clear how long the gold imported to Switzerland in May had been in Britain or to whom it belonged. Swiss customs does not share company names.

Britain, the United States, Japan and Canada agreed a ban on new Russian gold imports last month and the European Commission proposed one last week.

The London Bullion Market Association has meanwhile blocked trade in London of gold made in Russia after March 7 but says gold made there before that date can still trade.

“There is no place for Russian gold in Switzerland that is used to finance the war,” Robin Kolvenbach, CEO of Swiss refinery Argor Heraeus, told Reuters last week, adding that Argor had halted all business relationships with Russian counterparties after the invasion on Feb. 24.

Valcambi, another Swiss refiner, said this month gold could be imported from Russia legally under some circumstances and that Russian bullion made before the war began could be found around the world and legitimately imported.

Valcambi said it “has at no time taken delivery of gold produced in Russia after 7 March 2022.”

Kolvenbach said a gold import ban would have limitations: “The fundamental problem with gold is that it is like water, it always finds its way. If some states no longer buy Russian gold, others will still take it, even more so if they can get it at a discount because it’s harder to sell.”

(Reporting by Silke Koltrowitz and Peter Hobson; Editing by Michael Shields and Bernadette Baum)