Wells Fargo spokesman Mark Folk said in an email that the bank is cooperating in providing the requested information.
Justice Department Special Agent Supervisor James Hirt said in a 14-page affidavit seeking the search warrant that "there is probable cause to believe that employees of Wells Fargo Bank unlawfully accessed the bank's computer system to obtain the PII (personal identifying information) of customers."
"The bank's employees then used the unlawfully obtained customers' PII to commit false impersonation and identity theft by opening unauthorized accounts, credit cards and various other products that resulted in the accumulation of fees and charges for Wells Fargo," Hirt said.
One Los Angeles customer was surprised to learn last year that a Wells Fargo employee had opened a $10,000 line of credit linked to his accounts without his authorization, according to the affidavit.
Another was shocked when she and her husband began receiving notices from the bank on payments they allegedly owed on three life insurance policies they had never purchased. Bank employees repeatedly opened and closed her bank accounts, causing her to bounce checks and pay bank fees.
San Francisco is set to become the latest city to consider cutting ties with Wells Fargo in the wake of a growing scandal involving the creation of around 2 million phony bank accounts.
Supervisors Jane Kim and John Avalos introduced legislation Tuesday calling for the city to end its business with Wells Fargo and urging the city attorney and district attorney to investigate the bank's practices.
In addition, the legislation calls for the city to consider a "responsible banking ordinance" and revoke the naming of Wells Fargo Plaza at San Francisco General Hospital.
Kim called the bank's sales practices "outrageous and illegal."
"Instead of standing up for working people who should be valued as the backbone of its business, Wells Fargo decided to defraud its customers," Kim said.
"Big corporations want our business," she said. "It is up to us to use our leverage and power to ensure they are held accountable."
Wells Fargo, which is headquartered in San Francisco, has come under fire in the wake of revelations that sales staff created around 2 million fake accounts in an effort to meet high-pressure sales quotas.
Other cities and states, including Ohio, Chicago, California and Oregon, have also suspended ties with Wells Fargo due to the scandal, which has led to the firing of 5,300 employees and the resignation of CEO John Stumpf.
San Francisco Treasurer Jose Cisneros announced last month Wells Fargo would be dropped from the city's "Bank On" program, which helps connect low-income residents to low-fee accounts at banks and credit unions.