(Updates prices, adds poll, China coal) LONDON, Oct 27 (Reuters) - Aluminium dropped to its lowest in nearly eight weeks on Wednesday as falling thermal coal prices eased supply concerns. Coal prices slumped to their lowest in more than a month, hitting the daily 10% loss limit, after China’s state planner asked major coal-producing provinces to investigate and regulate illegal storage sites and to crack down on hoarding. China’s state planner added on Wednesday that it and the country’s market regulator had jointly formed four inspection teams to carry out “special supervision” of spot coal prices in key production regions and ports.] Aluminium smelting is energy-intensive and up to 40% of the metal’s production costs in China could be accounted for by power. The power crunch in China has underpinned aluminium prices and Commerzbank analyst Daniel Briesemann said that renewed scrutiny of the domestic coal market is behind Wednesday sharp price drop. A global shortage in magnesium, a key ingredient in aluminium alloys, has added to concerns, with analysts warning that this could result in demand destruction for lightweight aluminium used in automobiles and cans. Three-month aluminium on the London Metal Exchange (LME) was 5.7% lower at $2,667.50 a tonne by 1610 GMT after earlier touching its lowest since Sept. 1. RUSAL: Russian aluminium producer Rusal said the aluminium market deficit of 1.1 million tonnes in the first nine months of 2021 compared with a 2.2 million tonne surplus in the same period a year ago. INVENTORIES: Stocks of aluminium in warehouses monitored by the Shanghai Futures Exchange are at their highest since early July at 269,582 tonnes, weighing on prices. AL-STX-SGH On-warrant stocks in LME-registered warehouses are hovering at their lowest since 2019 at 621,150 tonnes. MALSTX-TOTAL POLL: Tightness in the aluminium market is due to ease next year, with the market deficit expected to more than halve next year to 396,000 tonnes from 893,000 tonnes in 2021, a Reuters poll found. OTHER METALS: LME copper shed 2.4% to $9,551.50 a tonne, zinc lost 2.8% to $3,329, lead fell 2% to $2,373, tin was down 6.7% at $34,925 and nickel ceded 3.2% to $19,435. (Reporting by Zandi Shabalala Editing by David Goodman, Kirsten Donovan)