UBS AG, reeling from record losses, says the U.S. Department of Justice is investigating whether the Swiss bank helped clients evade American taxes.One senior bank employee was ''briefly detained'' by U.S. authorities as a ''material witness,'' the firm said in an e-mailed statement. The Financial Times reported that the employee was Martin Liechti, the Zurich-based head of UBS's international wealth management business for the Americas.
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