More than 50 firefighters from across West Yorkshire tackled the fire at Parkam Foods in Haycliffe Lane, Wibsey, after they were called to the scene in the early hours of Saturday.
Half of the single storey building, which measured about 40
square metres, was ablaze when emergency services arrived at the site.
Around one fifth of the building, which was used for food processing and packaging, was destroyed and part of the roof caved in.
But firefighters managed to stop the blaze spreading throughout the whole building.
Crews were still at the scene damping down more than 10 hours later.
A West Yorkshire Police spokesman said the fire was being treated as suspicious.
Anyone with information is urged to call Bradford South CID on 0845 6060606.