The train line near Lake Street, Lurgan has been closed again on Sunday following a new report of a suspicious device being left along the track.
News from police that they had received another report came just after 2pm - two hours after police reported that the line had been reopened following the earlier security alert.
The closure of the rail near a rail crossing has caused Translink to cancel some services and organise bus substitution services between Portadown and Belfast.
The Enterprise service between Belfast and Dublin is experiencing delays of up to one hour.
It's the third security alert to have impacted on the the railway crossing n less than a fortnight, causing train delays and cancellations of services.
Police were called to the Lake Street area of the town on Sunday morning following reports of a suspicious object being found.
The alert caused significant delays on the line.
Translink had to cancel several train services and provide bus substitution services.
Thousands of passengers were affected by the earlier security alert on January 13 - mainly on the Belfast to Dublin Enterprise - in what police described afterwards as "an elaborate hoax".