A police spokeswoman said the businesses affected by arson were a commercial factory, a vacant premise and a food retailer.
During Labour Weekend the fire service was called to Heinz Watties at 2am on Monday morning where they extinguished plastic bottles and pallets, which were burning in the covered area.
Hawke's Bay senior station officer Collin Littlewood said earlier that the sprinkler had held the fire, which allowed it not to spread.
Also on Labour Weekend they responded to a fire in an empty building on Market St North where the Warehouse used to be housed.
The offenders had smashed the window and burnt a table and chair sitting in the large vacant place.
A small 3m by 3m shed beside the railway line opposite Watties was also burnt in the early hours of Friday during Labour Weekend.
Police want to remind business owners, managers and staff to protect themselves from crime wherever possible.
They said to ensure that buildings are secure, and valuable property is not left out when workers leave at the end of the working day.
Staff were also advised to check that alarms and CCTV systems were functioning well and cameras were cleaned and set correctly.
Police also said to remove items stacked close to fences, as it would eliminate opportunities to cross boundary fences.
Any suspicious activity or attempted break-ins should be reported as soon as possible to police.
Information can also be provided anonymously to Crimestoppers on 0800 555 111.