Wells Fargo & Co., already in the regulatory spotlight because of last year’s fake-account scandal, is drawing renewed scrutiny after a lawyer’s unauthorized release of sensitive client details for tens of thousands of accounts belonging to wealthy customers of its brokerage unit.

Regulators have started asking questions about the breach, according to a person with knowledge of the matter, after the data was mistakenly provided to an attorney as part of a lawsuit involving two brothers, one a Wells Fargo employee and the other a former employee. A person briefed on the matter said Wells Fargo has determined the accounts were all from one brokerage branch in the Northeast.

Representatives of the Financial Industry Regulatory Authority informally contacted at least one of the attorneys involved in the dispute for information about how the breach occurred and how Wells Fargo failed to detect it, said the person, who asked not to be identified because the matter isn’t public. Lawyers for the bank are taking steps to contact regulators about the data breach, according to another person with knowledge of the matter. The person didn’t specify which agencies.