The tunnel is being built over the line by Ipswich firm Jackson Civil Engineering to allow the construction of a new Tesco store - a development much opposed by local residents.
Independent engineering experts has thoroughly reviewed the tunnel design, the building method and the earth used as infill, which all form part of the overall tunnel design. They have agreed with Tesco and its consultants that the structure is safe for the passage of trains.
NR chief executive John Armitt said: 'Now we are satisfied that the tunnel is safe, our engineers have moved in and will be working night and day, rebuilding the track and signalling damaged in the tunnel collapse, to get trains moving once again.
'I appreciate the last seven weeks have been extremely frustrating for passengers. However we could not contemplate re-opening the line unless we were satisfied that the Tesco tunnel was completely safe.'