Firefighters spent the night tackling a large blaze in a derelict portable cabin.
Crews were called to industrial land off Wigan Road, near junction 25 of the M6 at Bryn, when large plumes of smoke could be seen at 1am on Thursday.
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The building was well alight when they arrived and six fire engines from stations across the area were needed.
They spent several hours working on the site and had to contain the blaze so the flames did not spread to neighbouring buildings.
Three crews remained there at 8am to continue damping down.
An investigation will be carried out to establish the cause of the fire, with one possibility being that it was started deliberately.