COLUMBIA, Mo. (AP) — A federal judge has ruled that a lawsuit filed against investment banker Morgan Keegan after the collapse of a proposed artificial sweetener plant in Moberly will be considered a class action.

U.S. District Judge Nanette Laughrey ruled Tuesday that class action is the most efficient way to resolve legal questions for investors in the failed Mamtek factory.

The Columbia Daily Tribune  reports an Alabama man sued Morgan Keegan and legal adviser Armstrong Teasdale in October 2012. The lawsuit seeks returns of investments from 133 people who bought $39 million in bonds between July 2010 and September 2011.

Morgan Keegan sold the bonds to investors to help finance the factory. The project collapsed when Mamtek went bankrupt and couldn’t make its bond payment.