A Chinese state-owned metals trader has sued units of Qingdao Port Group, the world’s seventh-largest port operator, as it seeks recovery of metals at the centre of a financing scandal in northeast China.

About two dozen Chinese and foreign banks and trading companies have already been battling over loans to Dezheng Resources, a private aluminium producer that allegedly used the cargoes of copper, aluminium and alumina stored in Qingdao as collateral to raise money. About $3bn is at stake.

The wrangle has raised concerns over the security of metals in other warehouses in China, and forced international banks to be more cautious about lending to Chinese importers using commodities as collateral. To date, there has been no evidence other companies or other bonded warehouses had issued multiple documents against the same metal to access loans.