The road was closed in both directions between Banbridge Road and Gowdystown Road for several hours on Wednesday afternoon due to a fire at business premises on nearby Rownatree Road.
Fire crews from Banbridge, Dromore, Lurgan and Lisburn Fire Stations were deployed to the incident and the road was shut for safety reasons as the blaze involved a gas cylinder.
A Northern Ireland Fire & Rescue Service spokesperson said: “Firefighters using thermal imaging cameras and firefighting jets dealt with the incident.
“The A1 dual carriageway was closed in both directions by Police Service of Northern Ireland who carried out traffic management during the incident.
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“Northern Ireland Fire & Rescue Service finished at the scene at 2:57pm and the incident has been passed through to the Health and Safety Executive for Northern Ireland.”