The Regent Street shop was destroyed by a blaze at about 12.30pm on May 13, forcing families to evacuate.
Part of the shop has since been demolished over fears for its safety although some nearby residents have been able to return home.
The cause of the fire, which shop owner Anthony Caswell-Jones said he thought started on the roof, has not yet been determined.
Three weeks on a spokesman for Northamptonshire Fire and Rescue Service confirmed it was not suspicious.
An exact cause is still being investigated.
Smoke billowed from the shop and was visible across the town before the fire spread with huge flames coming out of the shop’s frontage.
A nearby van was also destroyed by the fire.
Kettering Bedding Centre had run a business there since the late 1960s.
Last month the owners thanked the community for their support and said they hope to bounce back.
A shop statement said: “Our plan is to open a temporary shop as soon as possible and look to rebuild the bedding centre over time.”