Transfer of cenvat credit by NominatedAgency

A nominated agency imports metal for a specific customer based on terms finalised by the customer with overseas supplier.  Nominated agency pays import duty and clears the metal and transfer the material to buyer with its bill.

Duty was paid by the agency and the material is meant for the customer.

now how can the customer claim cenvat as the duty is paid by the nominated agency.

would like to know the relevant notification no. etc. for reference.

Thanks in advance.

P.kumar