Police are appealing for information after about 300 metres of copper powerline wiring was stolen from two power poles in Marton.

The poles, on Turakina Valley Road, were cut down in the early hours of Saturday 24 October, with the theft expected to cost about $500,000 to repair.

Police were made aware of the incident about 10am on the day after the damage caused a power outage near Christophers Road, Marton Prevention Sergeant Colin Wright said.

"Thefts of this nature are extremely inconvenient for not just the power companies but also the residents affected by the inevitable power outages," he said.

The 300m of wiring would have been difficult to conceal, and police believed someone may have seen the copper being moved or knew where it had gone.

"I want to remind scrap-metal dealers that it is illegal to purchase stolen copper or metal, and while it can sometimes be hard to detect, we urge you to report any suspicious sales or attempted sales to police immediately," he said.

Police are asking anyone who witnessed suspicious activity or had CCTV or dashcam footage from Turakina Valley Road and the surrounding area to get in touch.