Coking coal futures in China gained as much as 1.5% on Thursday, hitting their highest in nearly four months, as coal mines gradually suspend production ahead of the country’s Lunar New Year holidays and as imports plunged in December.

The most actively traded coking coal futures on the Dalian Commodity Exchange for May delivery closed 1.2% firmer at 1224.5 yuan ($177.72) per tonne, the highest since Sept. 23, 2019.“As the Spring Festival nears, local and state-owned coal mines are gradually suspending production and going on holiday, and the supply of coking coal in production areas have decreased,” said Huatai Futures in a note.

Meanwhile, recent trade data also aggravated supply concerns of the steelmaking ingredient. China’s coal imports in December slumped to 2.77 million tonnes, accounting for merely 13% of the 20.78 million tonnes in November, data from the customs showed on Tuesday.

Iron ore futures, however, slid after top steel-producing city Tangshan issued a fresh smog alert.Dalian’s benchmark iron ore contract, with May expiry, closed down 1.2% at 658.5 yuan per tonne.“As restocking ahead of the Spring Festival enters its tail-end, steel mills have sufficient inventories … Buying interest is poor,” added Huatai Futures’ note regarding iron ore.Dalian coke futures inched up 0.05% to 1,858 yuan per tonne.