A top US financial regulator has opened an investigation into whether Goldman Sachs Group Inc. improperly charged fees to execute some of its clients’ futures trades, the latest regulatory headache for the bank.

The Commodity Futures Trading Commission privately authorized sending subpoenas to Goldman for information about fees charged for some futures block trades, according to people familiar with the matter. The probe stems from a whistle-blower tip, said one of the people, who asked not to be identified discussing the confidential probe.