In the first incident, two 21-year-old men were arrested about 1am in central Dunedin after a member of the public noticed suspicious activity on scaffolding at Arthur St School.
Senior Sergeant Craig Brown said one man had been climbing on the scaffolding while another waited in a nearby utility vehicle.
When they were arrested, they had sections of copper spouting in their possession, he said.
Both appeared in the Dunedin District Court on burglary charges yesterday morning.
They were remanded to reappear on February 7.
About 4pm, police swooped on a Dunedin scrap metal dealer, escorting three people to the Dunedin Central Police Station.
Sergeant Chris George said the three people were arrested after trying to sell suspected stolen scrap metal.
They were being held in custody last night, and had not been charged.
The trio, two men and one woman aged in their 20s from Nelson, had driven south in the past few days, Sgt George said.
One of the men was wanted on arrest warrants issued in the Nelson District Court in November, he said.
Police were appealing for information regarding thefts of copper wiring in and around Otago and Southland, and sightings of a silver and blue 1986 Toyota Land Cruiser four-wheel drive vehicle.
The suspects' vehicle had been seized and would be examined this morning.
"A quantity of copper wiring has also been recovered. Investigators will be trying to match this with complaints in due course," Sgt George said.
