Dozens of firefighters have been tackling a fire at a store in Blackwood High Street.
The service says it started at around 2 o'clock this morning
There are no reports of injuries.
Firefighters were drafted in from Cefn Forest, Abercarn, Cardiff, Cwmbran and Merthyr.
Local residents are being asked to keep windows and doors shut.
The street's closed but other roads in the area are also likely to be affected.
More top news
A decent start to the day with sunny spells. Breezy in the west and feeling noticeably cooler.
Tributes have been paid after two Matalan employees were allegedly stabbed to death near the city centre store where they worked.
A damp start to the night with heavy rain spreading southwards. It will clear by the early hours to leave a dry start tomorrow.