NEW YORK — The scope of Wells Fargo’s fake accounts scandal grew significantly Thursday, with the bank now saying that 3.5 million accounts were potentially opened without customers’ permission between 2009 and 2016.

That’s up from 2.1 million accounts the bank cited in September 2016, when it acknowledged that employees under pressure to meet sales targets had opened accounts that customers might not have even been aware existed. People may have had different kinds of accounts in their names, so the number of customers affected may differ from the account total.

Wells Fargo said Thursday that about half a million of the newly discovered accounts were missed during the original review, which covered the years 2011 to 2015.

After Wells Fargo acknowledged the fake accounts last year, evidence quickly appeared that the sales practices problems dated back even further. So Wells Fargo hired an outside consulting firm to analyze 165 million retail bank accounts opened between 2009 and 2016.

Wells Fargo said the firm found that 981,000 more accounts were found in the expanded timeline, and roughly 450,000 accounts were found in the original window.

The scandal was the biggest in Wells Fargo’s history. The company ended up paying $185 million to regulators and settled a class-action suit for $142 million.