LONDON (Reuters) – Front-month futures on the blue-chip FTSE 100 spiked briefly to 6,700 points in heavy volume on Tuesday, before paring gains, in what several traders said was an accidental “fat finger” trade.

At 1511 GMT, the contract jumped 1.35 percent from 6,609.50 to 6,700 points before closing out the minute at 6,622.50 points.

“It was a fat finger,” said a London-based trader, adding that the size and volume of the move suggested “an institution was behind it.”

A spokesperson for FTSE was not immediately able to confirm the reason for the spike.

(Reporting by Simon Jessop and Sudip Kar-Gupta)