Elaina Patterson, 54, pleaded guilty to 31 larceny counts before Massachusetts Superior Court Judge Peter Lauriat over a scheme that lasted from 1999 to 2011 and targeted friends, family and the elderly, among others, Coakley said.

The judge also sentenced Patterson, a resident of Wilmington, Massachusetts, to 10 years probation to be served after the prison term, Coakley said.

A lawyer for Patterson did not immediately respond to a request for comment.

According to the attorney general, Patterson persuaded 15 family members and friends to invest nearly $4.5 million in accounts that she claimed carried high interest rates, and which she could set up by virtue of her position at a Bank of America branch in Reading, Massachusetts, about 14 miles north of Boston.

Starting in 2009, Patterson then stole almost $1.5 million from 16 other people, including a combined $315,000 from two 90-year-old customers, by forging signatures on withdrawal slips, in a bid to conceal her prior theft, Coakley said.

Investigators said they uncovered close to $6 million in fraudulent transactions, of which Patterson returned nearly $3.8 million to investors, leaving the total net theft at more than $2.1 million.

A Ponzi scheme occurs when money from new investors is used to pay earlier investors. Coakley said her office began probing Patterson's conduct after Bank of America referred the matter during an initial internal investigation.

(Reporting by Jonathan Stempel; Editing by Edwina Gibbs)

By Jonathan Stempel