"The LME has exercised its emergency powers to "suspend warrants issued in respect of metal held at WWS warehouses in the relevant locations as good delivery against LME contracts," the LME said.

"WWS now has warehouses in New Orleans, St Louis, Antwerp and Vlissingen...the warehouses in Singapore have already been closed and the metal transferred," LME said.

WWS was not available for immediate comment.

(Reporting by Pratima Desai; editing by Jason Neely)