European Union antitrust regulators are poised to levy massive fines against a group of global banks tied to their alleged attempts to manipulate benchmark interest rates, according to industry officials briefed on the discussions.

The fines are expected to be announced within the next month, one official said, bringing to an end a more than two-year antitrust investigation conducted by Brussels competition authorities into whether banks colluded to manipulate widely used benchmarks, such as the London interbank offered rate, or Libor, and its lesser-known cousin, the euro interbank offered rate, or Euribor.