PORTLAND – A supermarket clerk-turned-commodities trader was sentenced Wednesday to five years and 10 months in prison for masterminding a $6 million pyramid scheme that promised investors a return of up to 10 percent a week.

Edward W. Knipping, 55, of Boothbay, who pleaded guilty last September in federal court to charges of wire fraud, also faces five years of probation when he completes his prison term.

Knipping’s business, Time Traders Inc., was placed on probation and ordered to file documents proving it is out of business for good.

Using telephone, fax and e-mail messages, Knipping lured investors to Time Traders and Time Traders Investment Group, offering private membership open by invitation only.

He also encouraged investors to recruit others with promises to share up to 40 percent of any profit.

Between June 1999 and last May, he and his businesses raised more than $6 million from more than 1,300 investors in 40 states, Canada and Australia, prosecutors said.

During that period, Knipping faxed daily and weekly market summaries showing investor earnings of between 1 percent and 10 percent a week. Trading records, however, reflected losses of more than $1.3 million of the $2.47 million deposited into Knipping’s trading accounts between October 1999 and last April.

Of the more than $6 million raised from investors, only about $1.1 million remained in his accounts as of last June, according to court documents.

The court ordered that proceeds of previously seized assets derived from the fraud, including the $1.1 million and real estate in Texas, be applied against the amount of restitution.

Knipping, who had no formal investment training, had previously worked in sales and marketing and was employed most recently as a stock room clerk at Shop ‘n Save.

Prosecutors said this was Maine’s second-biggest case of investment fraud. The biggest involved Catherine Duffy Petit, who was sentenced in 1999 to more than 15 years in prison for masterminding an investment scam in which 140 Mainers lost nearly $8 million.