Thieves have targeted the "world's oldest railway" in Gateshead and put the restoration of a 116-year-old steam train at risk.
Police launched an investigation after copper pipework and brass fittings were stolen from Tanfield Railway's Sunniside base on April 28.
The fittings are likely to cost more than £20,000 to replace and have had an impact on the restoration of the Horden locomotive.
Detective constable Shaun Atherton, who is leading the investigation, said: “This was a targeted theft where thieves preyed on a charitable organisation during lockdown.
“The copper piping and brass fittings taken are antique and the parts are of great importance to the railway museum for restoration of the Horden locomotive salvaged from Horden Colliery.
“This theft has not only put back this historic restoration but left the Trust, who manage the railway, feeling dispirited and devastated during an already difficult situation fraught with financial losses from visitor income.
Tanfield Railway Trust chairman, Derek Smith, said: “We’re absolutely devastated by this callous and targeted theft. Our volunteers have put thousands of hours into the restoration of Horden.
"Before the lockdown it was only weeks away from hauling trains for the first time since 1972. The theft will put that back months and cost more than £20,000; money that we can ill afford at a time when we have no income.
“I’d urge anyone who thinks they might have information that could help catch those responsible to please get in touch with the police as soon as possible.”
Anyone being offered copper piping and brass as cut up scrap, or anyone who witnessed anything suspicious in the area, is asked to contact police via the ‘Report an incident’ page on the website quoting log 300 of April 28.
