Banks including Barclays that are enmeshed in the global investigation into potential manipulation of foreign-exchange markets are looking into the possible roles played by their salespeople, according to people familiar with the matter.

The focus on sales staff, part of the banks' internal reviews of their involvement in the probe, represents an expansion of an investigation that until now dwelled primarily on whether bank traders improperly worked together to influence currency markets, these people say. The possible involvement of salespeople could prove significant because they deal with external clients, as opposed to bank traders who mainly interact with other traders.