The shutdown in nickel trading is the biggest crisis at the 145-year-old exchange since a rogue Sumitomo trader tried to corner the copper market in the 1990s and tin trading was stopped for five years in the 1980s.

It underscores the market panic created by Russia’s invasion of Ukraine with buyers scrambling for the metal crucial for making stainless steel and electric vehicle batteries.

“The LME has taken this decision on orderly market grounds,” said the LME, one of the world’s top commodity exchanges, adding it was considering a closure of several days.

One reason the LME took action is because some position holders have been struggling to pay margin calls, traders said.

It raised margin requirements for nickel contracts by 12.5% to $2,250 a tonne, effective close of business Tuesday, and suspended trading of nickel on all venues for at least the rest of the day.

“The LME will actively plan for the reopening of the nickel market, and will announce the mechanics of this to the market as soon as possible.”

Three-month nickel on the LME more than doubled on Tuesday to $101,365 a tonne before the LME halted trade on its electronic systems and in the open outcry ring.

The explosive gains, which have seen prices quadruple over the past week, resulted from two major players facing off, said Malcolm Freeman of Kingdom Futures.

One entity has control of between 50% and 80% of LME inventories, LME data shows.

“There’s a very big short and a very big long who’ve been sparring. And because of their sparring, it’s brutalised so many other shorts,” said Freeman.

Some small industrial users have been caught in the crossfire, having taken positions to get physical delivery but then hit with margins calls costing millions of dollars, he added.

On Monday, the exchange said members with short positions, unable to deliver or to borrow metal at a backwardation of no more than 1% of the previous day’s cash price may have their delivery deferred.

The uncertainty caused by Russia’s invasion and resulting sanctions has added to an already bullish nickel market due to low inventories, which have halved on the LME since October.

Russia not only supplies about 10% of the world’s nickel but Russia’s Nornickel is the world’s biggest supplier of battery- grade nickel at 15%-20% of global supply, said JPMorgan analyst Dominic O’Kane.