Liffe cocoa futures dived through support on Tuesday afternoon after another bout of fund liquidation and closed about 5 percent weaker at a seven-week low, dealers said.
"Funds are offloading, mainly in New York, bringing London down," a dealer said. "There's been stop loss selling."
London's benchmark December contract snapped support around 897/900 and then 880 to end down 46 pounds at 877 pounds a tonne - a price not seen since mid July.
Turnover on the contract reached 5,956 from a daily tally of 11,148.
A break through 870 now put 840 in the firing line, one trader said.
Liffe's March contract also took a dive, finishing 4.9 percent lower at 901 pounds.
After recent declines about half the 30-percent gain built up in July during a fund-led rally has been lost.