European Union antitrust authorities are set to hit a group of major banks with heavy fines as soon as Wednesday for allegedly colluding to rig interbank lending rates, people familiar with the matter said.

The fines to be levied by the European Commission relate to alleged efforts to manipulate the euro interbank offered rate, or Euribor. The penalties could total several billion euros, people familiar with the matter said. The EU is expected to conclude that a handful of banks broke EU laws forbidding cartels and collusive behaviour, although the announcement could be delayed a week, these people said.