Scrap dealers in Derry and Donegal have been warned to exercise vigilance after a large quantity of lead was stripped from the old Thornhill College premises on the Culmore Road.
Sinn Féin Councillor Tony Hassan slammed those involved in the theft.
He said: “This is not opportunist small time thefts.
“It took place sometime on Thursday with the lead being stripped from the roof of the old school buildings.”
He asked for anyone with information about the theft to come forward and urged scrap dealers to be alive to thieves trying to get rid of stolen property.
“I would urge the PSNI to put in place whatever resources are available to apprehend whoever is behind these thefts, and if the community have any information on who is responsible they should bring it forward.
“I would also urge scrap merchants in the Derry and Donegal area to be wary of people trying to sell off lead material quickly,” he said.