The exchange, the world's oldest and largest market for industrial metals, said in a members' notice released on Friday evening that an unnamed trader first made a mistake then tried to cover it up by entering additional erroneous trades.

"The trader intentionally entered five orders in backwardation (when the market was in contango) hoping that they would be traded and then price adjusted in their favour in accordance with the LME Error Trade Policy," the LME said.

The LME, owned by Hong Kong Exchanges and Clearing Ltd., said one of the trades resulted in a loss to a third party, it added.

It said Mitsui Bussan Commodities, the commodities trading arm of Japanese bank Mitsui & Co., cooperated with the LME and took disciplinary action against the trader.

(Reporting by Eric Onstad; editing by Jason Neely)