LONDON/FRANKFURT - A global investigation into manipulation of interbank lending rates widened on Friday with Britain's fraud squad taking up the case and sources telling Reuters that Germany's markets regulator had launched a probe into Deutsche Bank. Authorities in the United States, Europe, Japan and Canada are examining more than a dozen big banks over suspected rigging of the London Interbank Offered Rate (Libor). Britain's Barclays has so far been the only bank to admit wrongdoing, agreeing last week to pay a fine of more than $450 million. The rate-fixing scandal has exploded into the front ranks of politics, especially in Britain, where politicians say the bankers responsible should end up in jail. Barclays CEO Bob Diamond was forced to resign this week and told a parliamentary committee that some of his firm's former staff could face criminal charges. The Libor rates, compiled from estimates by large banks of how much they believe they have to pay to borrow from each other, are used to determine interest rates on trillions of dollars worth of contracts around the world.