British prosecutors filed criminal charges Monday against three more former employees of Barclays, including two Americans, in the latest broadening of global authorities' investigation into alleged rigging of benchmark interest rates.

The UK's Serious Fraud Office said it charged Jay Merchant, a British citizen, and two Americans, Alex Pabon and Ryan Reich, with conspiracy to defraud for their alleged roles in manipulating the London interbank offered rate, or Libor. It declined to say when the alleged conduct took place. The SFO started a criminal probe into attempted interest rate manipulation in July 2012, shortly after Barclays PLC admitted wrongdoing and paid $450 million to settle rate-rigging allegations by US and UK authorities.