The Secretary of the Treasury shall deliver to the Commission, upon its request, samples of hazardous substances which are being imported or offered for import into the United States, giving notice thereof to the owner or consignee, who may appear before the Commission and have the right to introduce testimony. If it appears from the examination of such samples or otherwise that such hazardous substance is a misbranded hazardous substance or banned hazardous substance or in violation of section 1263(f) of this title, then such hazardous substance shall be refused admission, except as provided in subsection (b) of this section. The Secretary of the Treasury shall cause the destruction of any such hazardous substance refused admission unless such hazardous substance is exported, under regulations prescribed by the Secretary of the Treasury, within ninety days of the date of notice of such refusal or within such additional time as may be permitted pursuant to such regulations.