Copper prices dropped Wednesday the most in 19 months after a jump in inventories increased worries about an economic slowdown in China, the world''s largest consumer of the metal.

Copper futures for July delivery settled 3.49 percent lower at $2.5435 a pound, below their 50-day moving average for the first time since April 6 and their worst drop since September 2015. Prices of the metal continued falling in extended trade to near $2.53 a pound.

"I think the biggest thing is the worries about China," said Ryan McKay, associate commodities strategist at TD Securities.

"First we had a large build in LME copper stocks today, adding concern to the already elevated inventory levels," McKay said. "Also manufacturing data from China this week has come in below expectations, raising concerns around Chinese demand."

-18th China(Guangzhou)Int’l Non-Ferrous Metal（Copper）Exhibition