A man has been arrested on suspicion of arson in connection with a large warehouse fire in Daventry.
More than 50 firefighters were called to the building, owned by garden centre suppliers Gardman, in Parsons Road at 23:41 GMT on Sunday.
The roof appears to have collapsed and a plume of smoke could be seen for miles around on Monday afternoon.
Nobody is believed to have been injured but fire officers are expected to remain at the site for several days.
Deputy Chief Fire Officer David Harding, from Northamptonshire Fire and Rescue Service, said: “It will be some time yet before investigators can gain access to the building however, police have launched an arson investigation.”
He advised people living nearby to close doors and windows.
A number of surrounding roads at the Drayton Fields Industrial Estate have been closed by police.