There’s a mountain of iron ore sat right on China’s doorstep. Stockpiles at ports have climbed above 100 million metric tons, offering fresh evidence of increased supplies in the world’s top user that may hurt prices.

The inventories swelled 1.6 percent to 100.45 million tons this week, the highest level since March 2015, according to data from Shanghai Steelhome Information Technology Co. The holdings, which feed the world’s largest steel industry, have expanded 7.9 percent this year, and are now large enough to cover more than five weeks’ of imports.

Iron ore has traced a boom-bust path over the past two months after investors in China piled into raw-material futures, then changed course after regulators clamped down. While mills in China churned out record daily output in April to take advantage of a steel price surge, production in the first four months was 2.3 percent lower than a year earlier. Port inventories in China may continue to increase, BHP Billiton Ltd. forecast this week.

“There’s a lot of optimism actually that steel demand in China will increase,” Ralph Leszczynski, the Singapore-based head of research at shipbroker Banchero Costa & Co., said by phone. “It’s a bit of an ‘if’ as the economy is still quite fragile,” he said, calling the rise in port stocks “probably excessive.”

The raw material with 62 percent content rose 2.7 percent to $54.89 a dry ton on Friday, according to Metal Bulletin Ltd. Prices have tumbled 22 percent since peaking at more than $70 a ton in April, paring the gain so far in 2016 to 26 percent.

Imports by China increased 4.6 percent to 83.9 million tons last month from a year ago, according to customs data. The port holdings, which peaked at 113.7 million tons in July 2014, are above the five-year average of about 94 million tons. Last year, China imported 953 million tons, official data show, or about 18.3 million tons a week.

Goldman Sachs Group Inc. has warned that supply growth will accelerate this year, potentially feeding a glut and driving the commodity back to $40 by year-end. In April, miners in Australia including BHP, Fortescue Metals Group Ltd. and Roy Hill Holdings Pty shipped 37.7 million tons through Port Hedland, up 6.5 percent from a year earlier.

Port stockpiles in China, which have risen in 2016 even as demand rebounded, may continue to increase through the rest of the year, Vicky Binns, vice president of marketing minerals at BHP, told a conference in Singapore on Thursday. The expansion in low-cost seaborne output may go on to exceed demand growth in the short to medium term, Binns said.