Iron ore prices in China rose on Friday, with the benchmark futures contract extending a modest rally into a fourth session after some steel mills were reportedly allowed to resume sintering operations.

But steel futures dropped further, with construction steel rebar on track to post its first weekly loss in four weeks and the second so far this year, as concerns persist over a weak demand outlook amid high Chinese output.

The May 2019 iron ore contract, the most active on the Dalian Commodity Exchange, rose as much as 1.7 percent to 628 yuan ($93.33) a tonne.

Spot iron ore for delivery to China SH-CCN-IRNOR62, with 62 percent iron content, rose for a second day on Thursday to $87 a tonne from $85.50 the day before, according to SteelHome consultancy.

“The Chinese steel hub of Tangshan removed emergency restrictions on sinter plants, which had been in place since the start of the month,” ANZ said in a note.

Tangshan had last week extended a level 1 smog alert that was due to be lifted on March 6 due to unfavourable weather. That level is the highest in China’s four-tier pollution warning system.

Under such alert level, steel mills are required to curb output by 40-70 percent or even stop production, depending on the scale of their emissions.

Coking coal futures were also higher, with the benchmark contract up as much as 1.5 percent at 1,251 yuan a tonne. But coke edged down 0.9 percent to 1,981.5 yuan.

The most-active rebar contract on the Shanghai Futures Exchange dropped as much as 1.1 percent to 3,751 yuan a tonne. Hot rolled coil fell 1.9 percent to 3,656 yuan.

While near-term steel demand in China is expected to pick up as construction activity resumes after winter, the overall outlook is uncertain as the latest data suggest weakness in the world’s second-biggest economy.

“Investors continue to fret about Chinese demand,” ANZ said.

Data on Thursday showed growth in China’s industrial output fell to a 17-year low in the first two months of the year and the jobless rate rose, but property investment picked up.