(Portland, OR) -- A former Wells Fargo fraud investigator from Portland says the bank closed the accounts of hundreds of customers who might have been targets of fraud. Matthew Valles says Wells Fargo fired him in January after he filed internal complaints about what he called hundreds of mishandled fraud investigations in Portland. Banks are required by law to investigate whether criminal activity has happened when there are signs of fraud, such as a counterfeit check or an unauthorized withdrawal. Valles says rather than fully investigating, the bank just closed customers' accounts. He's suing Wells Fargo for violating whistleblower laws.