When Camden National Bank agreed to buy 15 Maine bank branches of Bank of America for $20 million, it got some extra accounts.

This week Bank of America sent letters to some Maine customers letting them know they would become Camden National customers on Oct. 26.

The branches included in the deal were Auburn, Brewer, Gardiner, Lewiston, Newport, Old Town, Rockland and Waterville, as well as three in Augusta and four in Bangor.

The letters listed checking, savings, IRAs, as well as business deposit accounts, safe deposit boxes and select business loans serviced by the banking centers as examples of accounts affected.

Some additional customers — who did not open accounts or transact business at those branches — also received letters that they were transferred.

Bank of America, which will have 18 branches in Maine after the transaction, said it could not disclose how many Maine accounts were transferred or why.

“We don’t disclose terms of the deal, and that includes criteria used to determine which accounts are impacted,” said Bank of America spokesman T.J. Crawford. “We have a specialized group of employees dedicated to assisting customers with any issues that arise from the transfer. When a customer brings a legitimate concern to our attention, we’ll work with Camden on a positive solution for all parties.”

Camden National, which will have 52 branches after the deal, did not return calls seeking comment.

The original deal included 15 Bank of America branches, but Camden National was required to divest a Rockland branch to resolve competitive concerns in that market raised by the U.S. Department of Justice’s Antitrust Division. Camden National previously said it expected to have $2.7 billion in assets and $2 billion in deposits after the deal.

Bank of America agreed to sell the Maine branches as part of a effort to cut 750 branches nationally. Bank of America has about 5,600 branches and about 56,000 small business and retail customers.