The Commodity Futures Trading Commission is investigating whether traders and brokers across Wall Street have manipulated prices on billions of dollars of contracts tied to interest rates, according to people familiar with the agency's probe.

CFTC officials have issued multiple subpoenas to banks and brokers involved in the setting of a benchmark daily rate set by a group of banks, the people say. The rate is primarily used to determine financial obligations between parties on either side of interest rate swaps, heavily traded contracts in which one firm typically swaps a fixed rate for one that floats.