U.S. regulators are widening their probe of global interest-rate-rigging by scrutinizing what they claim is a pivotal role of two U.K. brokerage firms in the scandal, the Wall Street Journal reported today. The Justice Department and Commodity Futures Trading Commission are examining ICAP PLC and R.P. Martin Holdings Ltd., so-called interdealer brokers that are go-betweens for banks seeking buyers or sellers for hard-to-trade assets. The brokers, both with headquarters in London, also help some banks decide their submissions for the London interbank offered rate (Libor) and other benchmarks that underpin trillions of dollars in mortgages and other financial contracts.