Fire crews are monitoring a smouldering pile of floor sweepings and chaff-dust in South Australia’s mid-north.

The Country Fire Service (CFS) says the fire was reported at a hay processing plant at Bowmans, about 10km east of Pt Wakefield just before 2am.

At the height of the fire, 18 firefighters and five fire trucks attended the blaze, which is burning about 100 metres from the nearest building.

The CFS says crews have established a fire break to protect a 2000 tonne stack of hay at the plant and they will continue to support staff who are monitoring hot spots in the pile.