Firefighters were called to a blaze at a disused council depot in Sheffield for the second time in four days.
Crews extinguished the flames in the building on Gayton Road, Pitsmoor, at 7pm on Tuesday.
They were also called to the same spot on Saturday night when another blaze was reported.
A police investigation into both fires is underway.
Firefighters were also called out to a blaze on Fenton Way, Rotherham, on Tuesday after a pile of rubbish was deliberately set alight.
And at 1.15am yesterday they dealt with a Ford Mondeo found burning on Drakehouse Lane, Beighton, Sheffield although the cause is not yet known.
Anyone with information about the council depot fires should call police on 101 or Crimestoppers on 0800 555111.