ISLAMABAD: The Oil Companies Advisory Council (OCAC) and the Directorate General of Oil of the Petroleum Division have warned of supply chain challenges and great financial loss to the oil refineries and state-run oil suppliers because of acute refining and storage capacity constraints as power sector backs off commitments. The rare warning by the DG Oil came a day after the Federal Board of Revenue (FBR) claimed before a parliamentary panel on Wednesday that major reason behind surge in import bill was increase in the import of refined petroleum products which could not be curtailed because of higher demand despite price hike.