Police say last year saw a 50 percent increase in burglaries involving copper and recyclable metals with more than $1 million worth of metal going missing over a six-month period.

Now - in a new scheme - police are working alongside the scrap metal industry to disrupt the surge of thefts.

Disruption, danger and damage

Church bells, railway infrastructure, power lines, gas pipes, even manhole covers.

It would seem that little is safe from thieves who put themselves at risk and cause millions of dollars worth of damage stealing copper, and other metals, all over the country.

Last month Canterbury police recovered nearly $200,000 worth of copper cable when they arrested a man discovered in a commercial property in Lincoln.

In March a man died after he was electrocuted in what police believe was an attempt to take copper from a transformer in Christchurch's Red Zone.

Further north, Bulls School principal Megan Symes said two men were interrupted by a staff member when they cut into live gas pipes while the school was closed for the weekend in July.

Symes said the damage cut heating to eight classrooms and could cost up to $20,000 to repair.

"Had our staff member not been on site, then that gas would have been flowing for another whole couple of days. Our grounds are used by our community, by travellers, our kids come and play here in the weekends. [It would] just take a spark and it could have been much worse," Symes said.

Jeff Harris of Wellington metal recycling firm Macaulay said the men - who staff later identified from a social media post - showed up at his Seaview yard soon after.

"They've got a small amount of material, looked like some off-cuts, they told a story and slipped through the cracks. What'd they have? They had four kilos of copper pipe. They probably walked away with about $60," Harris said.

Thefts might be linked to drug use

Harris said the yard typically made about a hundred purchases of materials each working day.

He said after more than 30 years in the business he believed the latest peak in stolen copper seemed most likely to be linked to drug use.

"I think people who are out there looking to steal metal and sell metal, it's basically to fund the next hit. Our staff will see people come in who look like they're under the influence. They might just look at what material they've got and say 'sorry, we're not actually buying that material today, thanks' and off they go.

"I just don't think we had the drug problem in the community years ago that we have now.

"There's a lot more desperation and risk that people are prepared to take. For what? A few dollars worth of copper and it's not only copper, it's whatever they can get their hands on," Harris said.

His Seaview yard had nearly 100 cameras installed and any cash payments were made via an ATM installed on site.

But even the scrap buyers themselves are not immune to the problem.

Last year a Macaulay site in Tauranga was targeted by a brazen daylight thief.

"We got the guy later on camera. He climbed onto our roof, stayed up there all day and took one of the big copper electrical cables.

"That had a fairly limited scrap value, but what did it do for us? He over-currented all of our switchboard and that fried all the circuitry and our heat pumps and before we knew it, we had a $100,000 insurance claim," Harris said.

President of the New Zealand Association of Metal Recyclers Spencer Trillo said, under the Second-Hand Dealers and Pawnbrokers Act 2004, scrap dealers were required to log sales and the seller's identification. Staff also recorded the registration of any vehicles coming into their yards.

However, thieves breaking down stolen materials made it nearly impossible to link the metal to reported burglaries.

"Traditionally to prosecute someone for stolen goods, you'd either have to catch them in the act or you have to catch them with those stolen goods. But the onus is on the police to prove that stuff has come from that exact location. It's a very high threshold for them to prove, near on impossible once these people have gone and destroyed the metal beyond recognition.

"So you just see a constant circle of they know these people are doing it, they know it's happening, but they can't prove it," Trillo said.

New scheme on trial

But a new scheme being trialled in Christchurch was allowing police to analyse patterns and trends by having metal recyclers share details of their purchases with police en masse.

"So, we're now handing over all that information to them and they're able to run it through AI and start picking out these people who are selling to multiple businesses - who have been flying under the radar - and they're able to target them in this way," Trillo said.

Detective Sergeant Michael Hawke of the Canterbury Criminal Investigation Branch said Operation Scrap was launched at the beginning of the year.

"The operation involves the monitoring of transactions across all metal recycling businesses within the district. By analysing transaction data alongside information held within police intelligence systems, investigators are able to identify suspicious activity, detect potential disposal of stolen metal, and monitor persons of interest with a history of dishonesty offending," Hawke said.

He said the response from recycling businesses had been "overwhelmingly positive".

"These businesses do not want to be trading in stolen property and are actively monitoring for suspicious transactions. Through the sharing of information and transaction histories, police are able to go a step further by using intelligence to identify persons of interest and prevent offenders from continuing to trade.

"These are legitimate businesses with reputations and livelihoods to protect. Accepting stolen metal places their licences and businesses at risk, and there is a clear commitment across the industry to prevent this from occurring," Hawke said.

The pilot scheme would be rolled out for consideration by other districts once any issues were identified and resolved.

"Police have a clear message for those responsible for the theft and burglary of copper and scrap metal in Canterbury: every transaction is being monitored, and it is only a matter of time before you are identified and prevented from trading.

"Through the combined efforts of police and the recycling industry, opportunities to profit from stolen metal are rapidly diminishing," Hawke said.