Sometimes the supply chain from the extraction of virgin material to the complete assembly may be very long and difficult to document. When documenting regional materials, how far do I have to go in the supply chain?

Let's for example consider a manufacturer of precast concrete elements, located within the 500 mile boundary. The factory buys the reinforcement steel from a steel factory, also located within 500 miles. However, the raw material used for making the reinforcement steel is extracted outside of the 500 mile boundary. Does the steel constribute to the regional materials credit in this case?