Forestry SA says it is resorting to installing surveillance cameras and other monitoring devices in a bid to stop the theft of fuel from machinery in forestry areas.

Last week, police raised concerns about escalating reports in the lower south-east, urging contractors and farmers to keep their equipment locked and out of sight.

Forestry SA's Michael Bleeby, the manager for sales in the Green Triangle region, says the impact is far reaching for logging contractors, who are faced with unnecessary downtime and considerable costs.

"Fixing up equipment that's been damaged and recovering from that situation. The dollar impact of fuel losses and so on," he said.

"They bring fuel out to the bush each day in bulk tankers, but the equipment that remains in the forest overnight has still got fuel in the tanks and that tends to be where the damage and fuel theft occurs. We're talking hundreds of litres when it happens."