Police allege the 19-year-old robbed the Kingsley's Chicken store in Weston on Wednesday, aided by a second man.

They allege the men, who had their faces covered, used a machete to demand cash from chicken store staff, before fleeing in a stolen car.

Police arrested the teenager on Saturday, but say they first took the suspects into custody 30 minutes after the robbery before they were released.

Police say they subsequently found the stolen car in Chapman, with the stolen cash drawer and other evidence.

Authorities raided a Rivett home and say they found a machete hidden in a dog kennel.

Meanwhile, in a separate incident, a 15-year-old was detained by members of the public after an alleged aggravated burglary in Duffy.

Police say an 18-year-old member of the public chased and tackled the boy to the ground after an alleged burglary at Duffy shops early Sunday morning.

The 15-year-old will face the ACT Children's Court today.

And in a third unrelated incident, police arrested a 25-year-old woman at a Caltex Service Station in Hughes.

It is alleged she tried to use a cigarette lighter to set fire to some spilled petrol, threatened several people and damaged a vehicle.

She was charged with property damage and a charge relating to arson threat, while police say further charges are likely.

The woman will face the Magistrates Court on Monday.

Anyone with any information on the three incidents is being urged to contact Crime Stoppers on 1800 333 000, or via the website.