Fire crews were called to the Johnson St property, after a shed containing building materials and supplies went on fire about 6pm.
Fire risk management officer Stuart Ide, accompanied by CIB detectives from Balclutha, investigated the cause of the blaze yesterday.
Mr Ide said the fire was deliberately lit.
Constable Brian McKinney, of Balclutha said no trace of accelerant was found but rubbish, paint tins, and other dry material created plenty of fuel for the fire.
It took more than 10 firefighters two and a-half hours to contain the blaze, which started in a lean-to before spreading to the nearby shed.
The fire had similarities to three other blazes in the past nine months and police believed the same person could be behind all four, Const McKinney said.
An investigation into a fire at the property last December could not determine if it was started deliberately as a large amount of hay had been stored there. About two days later grass was intentionally set alight on Johnson St, he said.
On April 20, an unoccupied house in the Fulton Hogan yard in Scott St, Milton, was destroyed by fire. It was treated as suspicious, as the transportable single bedroom home had been unoccupied for two years and had no electricity.
In each fire an accelerant was not used and happened in a small area.
Police are following strong leads and anyone who saw anything suspicious in the area should contact Balclutha police on 418-0203.
