A suspicious package sparked a security alert in Lisburn in the Linenhall sorting centre on Friday morning.The alert has since ended and the cordon lifted.A PSNI spokeswoman said: "A viable device was made safe and has been removed for examination."It comes after a letter bomb was discovered in a Royal Mail centre in Londonderry on Thursday.The sending of explosive devices via the postal system is of great concern to Royal Mail.Royal MailUTV understands both packages are believed to have been addressed to Maghaberry Prison, Northern Ireland's high security jail.Police and the Department of Justice have declined to comment on who the packages were addressed to.The First and Deputy First Ministers have condemned those behind both incidents.In a joint statement, Peter Robinson and Martin McGuinness said: "We utterly condemn the recent letter bombs discovered in postal sorting offices in Derry/Londonderry and Lisburn."The people behind these letter bombs are opposed to the democratic will of the people and want to drag us back to the past."They have no respect for the postal workers, the wider community or the future."Justice Minister David Ford said the suspicion was that dissident republicans were behind the attacks and said the incidents were similar to those attacks on army recruitment offices in England.Imagine if it was a child or a postman that got caught up in the blast.David FordThe Alliance man added: "We are to an extent lucky, these are crude devices, but they are viable and they could potentially kill."Mr Ford would not comment on who was targeted in these incidents. He added: "The reality is, this is targeting the entire community."Spokesperson for Royal Mail, Barbara Roulston said :"These incidents are being investigated by the police and we are doing everything we possibly can to facilitate their investigation."We are doing everything we possibly can to protect our people as they go about their daily jobs serving communities across the United Kingdom."Royal Mail has rigorous procedures in place to deal with suspect devices and trained personnel who manage these situations. Our procedures are under constant scrutiny and review and our employees are regularly briefed on these types of issues."Police have warned people to be vigilant and report suspicious packages immediately.