The cause of a fire which devastated two commercial premises on a Doncaster business park is still under investigation.
But the blaze which took almost half a day to deal with is believed to have been the work of an arsonist.
Up to 13 fire engines and around 70 firefighters were called out to deal with two large incidents in Armthorpe on Saturday, and reinforcements were also sent from another county.
South Yorkshire Fire and Rescue Service were first called to reports of a fire at a pallet yard on Cow House Lane, Armthorpe, at around 1.30am.
It is believed that several thousand wooden pallets were on fire.
Firefighters used water and foam to try to extinguish the blaze.
But the heat from the flames was so intense that it started a second fire at nearby premises.
More firefighters from other Doncaster stations were sent to the second incident, at nearby West Moor Park Network Centre on Yorkshire Way, which broke out at around 2.45am.
A single-storey industrial unit 20 metres by 60 metres was on fire.
Fire engines from across Doncaster and South Yorkshire were on the scene of both incidents, plus two fire engines from Goole in Humberside.
No one was hurt in either incident and the fires did not affect any homes in the area, although some roads leading to the industrial estate were closed for a time.
“Wooden pallets burn really easily when they get going and our concern was that radiant heat might spread to other buildings on the estate,” said a spokesman.
Both fires were brought under control by 8am but relief crews remained at the scene until Saturday evening to complete damping down operations.
An investigation into the cause of the first fire started after they had been dealt with.
The spokesman added: “The cause of the pallet yard fire has been recorded as deliberate, whilst the industrial unit has been recorded as accidental, most likely due to radiant heat from the pallets fire or embers.”
n Fire crews dealt with another deliberate fire in Doncaster.
They were called out to The Avenue in Bentley at 11.30pm on Monday when rubbish was set on fire in an alleyway.