The old Albion Flour Mill will be demolished after being gutted by fire believed to be deliberately lit.

A large crack appeared down the length of the southern wall of the old brick building soon after the fire was extinguished, prompting fears it would collapse.

Demolition crews have since been called in by Brisbane City Council engineers.

The four-storey Albion flour mill, in Brisbane's inner-north, has long been considered one of the city's landmarks.