An internal Credit Suisse investigation into allegations of inappropriate employee behaviour has roiled the bank's European stock trading desk, according to people familiar with the probe, in the latest example of a major bank uncovering potential problems as it sifts through employees' electronic communications.

A veteran trader on the European equities sales desk, which serves as a hub for the bank's relationships with major hedge funds and other asset managers, has been suspended since February, the people said. Her boss, a managing director who runs the London desk, also went on leave this summer in connection with the probe, they said.