Police are investigating whether a fire on vacant land near the Tuggeranong Parkway at Curtin was deliberately lit on Sunday afternoon.
ACT Fire & Rescue and the ACT Rural Fire Service were called to the location, south of Cotter Road and to the east of the Tuggeranong Parkway, about 5pm.
"Police attended to manage onlookers and are now speaking to witnesses as the fire may have been deliberately lit," a spokesman for ACT Policing said in a statement.
Anyone with information about the fire has been asked to contact Crime Stoppers by telephoning 1800 333 000.
A spokeswoman for the Emergency Services Agency said the fire had grown to 10 metres in size but had been brought under control and would take time to be extinguished.
Heavy rainfall in the ACT earlier this month was expected to buy time against the threat of grassfires before a run of hotter, drier days.
ACT Rural Fire Service chief officer Rohan Scott on October 4 said forecasts of below-average rainfall and above-average temperatures would deliver significant grass growth through spring, contributing to the risk of fast-moving grass fires.
"That will be our biggest risk as we move into the summer period. As we enter into the new year, our forest fuels will start to dry out and they'll become a risk in the forested areas too," Mr Scott said.
