Former News of the World chief reporter Neville Thurlbeck has been released on bail tonight pending further enquiries.
He was arrested earlier in central London by detectives investigating phone-hacking at News International, Scotland Yard said.
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An inquiry will be carried out by the Aircraft Accident Investigation Bureau.
President Michel Aoun, in office since 2016, said he was first told of the dangerous stockpile nearly three weeks ago.
Taoiseach Micheal Martin announced new restrictions for midland counties on Friday following a surge of coronavirus cases.