At least five Wells Fargo employees had sued the San Francisco-based bank or filed complaints with U.S. regulators alleging they were fired after reporting unauthorized openings of checking and credit card accounts for clients by bank employees, according to a Reuters review of lawsuits and complaints to the U.S. Labour Department.

U.S. prosecutors in San Francisco subpoenaed Yesenia Guitron, one of the highest-profile whistleblowers, in December to compel her to testify before a grand jury. [nL1N1EI14W]

The internal report commissioned by Wells Fargo's board and prepared by law firm Shearman & Sterling said on Monday that there was no systematic retaliation against employees who spoke out about the sales practices. [nL1N1HI0D1]

"Based on a limited review completed to date, Shearman & Sterling has not identified a pattern of retaliation against Community Bank employees who complained about sales pressures or practices," a footnote in the report said.

The review of the cases is ongoing, the report said, and has included files for nearly 900 ex-employees who were fired within a year after calling in a tip to the bank's ethics hotline or within a month of the bank disclosing in a $185 million settlement in September that employees had opened as many as 2 million accounts without customer permission.

In total, 5,300 employees were fired over the sales practice abuses.

Investigators found no evidence of retaliation in the cases of 11 ex-employees who were publicly identified as whistleblowers in media reports, according to the report.

Stuart Baskin, the lawyer from Shearman & Sterling who led the investigation, said the firm was still investigating reports of retaliation but that he did not expect the conclusion to change.

The report said Shearman & Sterling is completing reviews of nine employees who reported being fired after calling Wells Fargo's ethics line phone number to submit tips about unethical sales practices.

(Reporting by Elizabeth Dilts and David Henry in New York; Editing by Meredith Mazzilli)

By Elizabeth Dilts and David Henry