Iron ore prices that were jacked up by China’s speculative frenzy last month just took another steep leg down. Futures plummeted in Asia on Monday as rising port inventories in the top user spurred concern that global supplies are once again topping demand.

In Singapore, the SGX AsiaClear contract for July settlement sank as much as 5.7 percent to $46.03 a metric ton and traded at $46.34 at 1:48 p.m. in Singapore, while futures on the Dalian Commodity Exchange fell as much as 6.7 percent to the lowest since February. Miners’ shares retreated in Sydney, with BHP Billiton Ltd., Rio Tinto Group and Fortescue Metals Group Ltd. all lower.

Iron ore has been on a tumultuous ride this year as investors sought to gauge conflicting economic signals from Asia’s biggest economy against still-elevated port stockpiles. In China, traders piled into raw-material futures including iron ore in March and April, helping to boost prices, only to switch track when regulators clamped down. Inventories at ports have climbed above 100 million tons, offering fresh evidence of increased supplies from Australia and Brazil, and BHP forecast last week that there may be further increases.

“Stockpiles have once again broken the 100 million ton-level, indicating that supply pressure has increased significantly,” Fan Lu, an analyst at Sinosteel Futures Co., said in a note on Monday. “Mills’ margins have narrowed as steel output recovered,” suppressing demand for iron ore, she said.

 

 

Iron ore with 62 percent content was at $54.89 a dry ton on Friday, 22 percent below the peak of more than $70 in April, according to Metal Bulletin Ltd. The port inventories swelled 1.6 percent to 100.45 million tons last week, the highest level since March 2015, according to data from Shanghai Steelhome Information Technology Co. They’re up 7.9 percent this year.

As iron ore has sunk, other steel-making raw materials and products have also retreated. Rebar futures in Shanghai dropped as much as 6.4 percent on Monday to 1,930 yuan ($295) a ton. Most-active prices had rallied to as much as 2,787 yuan about a month ago. Coking coal futures in Dalian plunged.

Goldman Sachs Group Inc. was among banks that said the prices seen during the speculative frenzy would not last as oversupply was likely to return. Last week, Vale SA’s Claudio Alves, global director of iron ore marketing and sales at the Rio de Janeiro-based mining company, said there was a need to prepare for tougher times ahead.

Australia and Brazil will export a combined 1.24 billion tons this year, from 1.13 billion tons in 2015, according to Australia’s Department of Industry, Innovation & Science. As Australia’s top miners boost output this year, smaller rivals are also raising supply. Atlas Iron Ltd., a junior based in Perth that’s partly held by Glencore Plc after a revamp, said Monday that it shipped a record volume in the first three months of this year.

“Australia and Brazil have kept shipments at relatively high levels,” said Zhao Chaoyue, an analyst at China Merchants Futures Co. in Shenzhen. “Shipments will probably continue at high levels without many hiccups. Port inventories in China will continue to accumulate.”