China’s imports of copper surged over 19.4% during May compared to the same month last year to more than 430,000 tons, showed data released by customs on Wednesday.

The copper imports swell the already ample supply China already has that should reduce the amount of metal imports during the upcoming months.

Shipments of copper into China have stayed strong in 2016, up over 22% the past five months, after a weaker U.S. dollar boosted the purchasing power of China, swelling the bonded and exchange inventories. In March, record highs were hit in the exchanged stockpiles.

During the same time, smelters in China have increased their copper concentrate imports and restarted their production as an increase in the global supply in mines has given them an opportunity to increase processing fees.

Copper imports during May dropped by 4.4% from April. At the time, imports of the copper concentrate that is used in smelters soared 13% over the month before and were 45% up from the same time last year.

Overall, copper imports in China are going to further ease in June as rising refining and treatment charges and production of domestic smelting will increase the supply domestically and lower the import demand, said an industry analyst.

A week ago, Jiangxi Copper from China and BHP a global miner agreed to $100 per ton for TC and 10 cents per pound for RCs, above the terms that had been agreed to last December by Jiangxi and Antofagasta a miner of $97.35 and 9.375 cents for the 2016 full year.

Imports of copper concentrate for the five months to start the year rose by 34% for the year.

The rising supply had hurt demand for copper known as spot refined, already hurt by a slowdown in the economy in the top producer of the metal in the world.

Premiums for spot copper in the bonded zone of Shanghai reached lows of four years at $45 per ton during this week.

Traders in China have shifted their surplus copper to warehouses in Asia, depressing the global price.

The data released by Chinese customs also indicated that China increased its exports of aluminum during May to over 420,000 tons an increase of 5% from April of 2016 and an increase of 2.4% compared to April of 2015.

Nevertheless, exports of aluminum remain down more than 7.9% at 1.9 million tons through the first five months of 2016.