Wells Fargo, already struggling to rebuild its reputation after a scandal over the creation of fraudulent bank accounts, signaled on Friday that it could have more bad news coming.

The bank said in a regulatory filing that its review of potentially unauthorized accounts could reveal a “significant increase” in the number of accounts involved, up from the 2.1 million that it previously estimated. Wells Fargo said it had expanded its investigation to add three years to its review period, which covered accounts opened from 2011 to mid-2015.

But Wells Fargo also indicated that it has a new regulatory issue looming: an investigation by the federal Consumer Financial Protection Bureau into whether customers were harmed by the bank’s practice of freezing, and in some cases closing, bank accounts suspected of being affected by fraudulent activity.

That issue had not been previously disclosed, according to Timothy J. Sloan, the bank’s chief executive, who mentioned it in an unusual public statement drawing attention to his company’s regulatory filing. In the statement, he also detailed the bank’s efforts to reassure its customers.