Shares in commodities giant Glencore have plummeted to a record low after warnings over the price of metals.
Glencore's shares plunged 30% to just 67p per share as analysts said the company's huge debts could render it worthless if metal prices continue to fall.
Investec's warning sparked more than £3.5 billion being wiped off Glencore's value.
Glencore is hoping to raise around $12bn by selling its agricultural business, but Investec said "valuing such a volatile business is likely to be tough" and therefore raised doubts over how much it could raise.
Hunter Hillcoat, an analyst at Investec, said: "Mining companies gorged themselves on cheap debt in a race to grow production following the Chinese stimulus that occurred in the wake of the great financial crisis.
"The consequences are only now coming home to roost, as mines take a long time to build."