Chinese iron ore futures tumbled 8 percent on Thursday, to their biggest single-day fall in more than five months, on concerns that demand for the raw material was at risk from slower steel consumption.

Shanghai rebar steel slumped more than 6 percent while other steelmaking raw material coking coal also slid.

China’s crude steel production reached a record 72 million tonnes in March and there were indications that output remained high through the first 20 days of April, said Wang Di, analyst from CRU consultancy in Beijing.

As steel prices dropped last month, though, some Chinese mills pushed forward their maintenance schedules to somehow manage output, said Di.

The most-active rebar on the Shanghai Futures Exchange fell 6.2 percent to close at 2,931 yuan ($425) a tonne, after sliding by its exchange-set floor of 7 percent earlier.

Iron ore on the Dalian Commodity Exchange dropped 8 percent to end at its downside limit of 485 yuan per tonne, marking its biggest daily drop since Nov. 16.

“We are bearish,” said Di on her outlook for iron ore prices. Demand this month “could be even worse than now or compared to end-April,” she said.

Iron ore shipments to China from Australia’s Port Hedland terminal, used by top miners BHP Billiton and Fortescue Metals Group, rose to 34.86 million tonnes in April from 31.5 million tonnes in the previous month, port data showed on Wednesday.

Inventory of imported iron ore at China’s major ports reached 130.55 million tonnes as of April 28, up 950,000 tonnes from the previous week, SteelHome said. The stockpiles hit 132.45 million tonnes in March, the most since SteelHome began tracking it in 2004.

Thursday’s plunge in futures could drag down spot iron ore prices again after they had stabilised in the past two days.

Iron ore for delivery to China’s Qingdao port .IO62-CNO=MB was little changed at $68.68 a tonne on Wednesday, according to Metal Bulletin.

Coking coal futures on the Dalian exchange fell 5.8 percent to 1,049.50 yuan a tonne, while coke dropped 6 percent to 1,493 yuan.

Source: Reuters (Reporting by Manolo Serapio Jr.; Editing by Tom Hogue and Sherry Jacob-Phillips)