Three people have been arrested after police allegedly caught them in the act stealing wooden railway sleepers from a disused railway line north of Adelaide. 

Police say the arrests were thanks to a call from the public – one of many calls in recent months reporting suspicious behaviour of a similar nature in the Gawler and Barossa region.

Barossa Criminal Investigation Branch officers and members of the Gawler Police attended the railway line on the Gawler Belt near Twartz Road.

"Officers located two men and a woman removing railway sleepers at that time from that railway line," Senior Sergeant Robert Mowday said.

A 44-year-old Payneham South man, a 50-year-old Waterloo Corner man and a Felixstow woman, 47, were arrested and charged with theft and property damage.

The men were bailed to attend the Elizabeth Magistrates Court in July while the woman was refused bail.

Senior Sergeant Mowday said police were investigating possible links involving multiple thefts that occurred on the same disused railway line in recent months.

"Back in March, a theft was reported to Barossa Criminal Investigation Branch, and they had carriage of that investigation and put out a media release requesting public assistance and vigilance," he said.

He said there has been a string of thefts from the railway line.

The rail freight operator that owns the track, Aurizon, has been contacted for comment.

Firewood warning

Senior Sergeant Mowday warned people to be careful where they source their firewood.

"We'd recommend that anyone be suspicious of anything on social media that doesn't look professional in regard to selling firewood, and to question of course any chopped railway sleepers," he said.

"We know that many of these railway sleepers are contaminated to some extent with herbicides, grease and oils, so when they're burnt they have the potential to release harmful fumes."

He urged anyone with information on railway sleeper thefts to call Crime Stoppers.