Greek authorities say they are cooperating with Belgian authorities on an investigation , and on Sunday Belgium requested the extradition of one of the suspects arrested in Greece . Neither France nor Greece confirms whether the probe involves a jihadi cell in Verviers . Source : Up to 20 sleeper cells may be expected to operate in France , Germany , Belgium and the Netherlands .
Neither France nor Greece confirms whether the probe involves a jihadi cell in Verviers . Source : Up to 20 sleeper cells may be expected to operate in France , Germany , Belgium and the Netherlands .