A fire that damaged a magazine printers may have been started by intruders, says the firm.
A fire service investigation has begun into the blaze at the paper warehouse at Pensord Press at Pontllanfraith, Caerphilly, at about 0223 GMT.
Managing director Darren Coxon said initial findings suggested someone may have lit a fire.
A Gwent Police spokesperson said: "We are treating it as suspicious and are investigating."
Mr Coxon said no-one was injured and that production was continuing as normal.
Crews from Cefn Fforest, Abercarn and Caerphilly fought to contain the blaze.
A fire service spokeswoman said around 10% of the building was damaged by fire and the rest suffered smoke damage.
Mr Coxon said: "The fire was started at around 2am on Thursday morning in our paper warehouse, which is in a separate building to the main print facility in Pontllanfraith.
"Initial indications are that unauthorised people broke into the property early this morning and lit a fire, damaging some of the paper pallets and an office."
Pensord is a sheet-fed magazine printers, and operates out of a 50,000 sq ft (4,645 sq m) factory.
The plant, which operates 24 hours a day, employs more than 140 people.