The suspect packages sent to Army Careers offices were in A4-sized envelopes, postmarked Ireland, contained black powder which was explosive and if ignited would have caused flash burns, ITV News' Juliet Bremner understands.
However, the officers who discovered the suspect packages are not certain that they would have exploded.
This indicates that Irish dissident groups were very likely behind the attack.
More top news
Average household incomes have returned to around the levels they were at before the financial crisis hit, new analysis indicates.
Figures uncovered by a Freedom of Information request reveal one university leader received £623,000 in 2013/14.
Tens of thousands of students are not achieving their potential in state schools, a highly-critical Ofsted report has said.