In construction site theft normally occur when subcon are not paid

The subcon usually hold their worker wage if no payment then the worker will steal materials and equipment to recoup their loss wages

Stealing from construction site require some insider cooperation, normal drug addicted mat pet won't be able to do it

Someone with valid permit won't steal it, someone with nothing to lose will. The workers that are not paid months in wages will be desperate enough to pull this stuff.

You not familiar with construction theft, sometimes a heavy steal beam few tonnes also can be stolen from the site. It's impossible to be done by outsider. Only insider can do that.