London: Aluminium touched a three-month peak on Tuesday after major producer Norsk Hydro was hit by a cyber attack, causing its giant smelters to switch to manual operation and some extrusion plants to be shut.
Other industrial metals also gained ground on optimism about easy monetary policy ahead of a US central bank meeting and on hopes for further stimulus in top metals consumer China.
Aluminium prices spiked after Hydro said the IT systems for most of its activities had been affected.
"The trigger was the news from Hydro about their production problems after the cyber attack, and since aluminium is the metal with the biggest short position, there was probably short covering taking place," said Gianclaudio Torlizzi, partner at consultancy T-Commodity in Milan.
Benchmark aluminium on the London Metal Exchange hit a high of $1,944 a tonne, the strongest since 18 December, before paring gains to trade at $1,934, up 0.7%, in official open outcry trading.
Aluminium inventories: Helping to cap gains in aluminium was a 17% jump in on-warrant LME inventories, stocks not earmarked for delivery, to 761,425 tonnes, daily LME data showed on Tuesday.
Fed meeting: Base metals joined rising world shares as risk appetite increased, with investors betting on a dovish statement from the US central bank on Wednesday.
Torlizzi, however, was cautious. "If you stick to the economic data, there shouldn't be so many reasons to be bullish," he said. "The market is running the risk of being disappointed tomorrow, which could translate into downside pressures."
Copper: Three-month copper gained 0.9% to $6,485 a tonne in official rings after a union at Chile's Sierra Gorda copper mine, controlled by Polish mining company KGHM , said it could strike this week after rejecting the latest offer in contract negotiations.
Technicals: LME copper may test resistance at $6,525 per tonne this week, a break above which could lead to a gain into the range of $6,594-$6,662, according to Reuters technical analyst Wang Tao.
Nickel: A rise in Chinese steel and iron ore prices supported nickel, mainly used to make stainless steel. LME prices climbed 1.9% to trade at $13,180 a tonne in official activity.
Philippine nickel: Nickel Asia Corp, the Philippines' top nickel ore producer, expects its 2019 shipments to be unchanged from last year, although it plans to increase its domestic sales to maximise profits.
Prices: Zinc gained 0.8% to $2,803 a tonne in official trading, lead, untraded in rings, was bid down 0.2% at $2,036, and tin added 0.2% to trade at $21,225.