Power to summon persons to give evidence and produce documents; attendance and production required, with statutory privilege protection. Gazetted officers of Customs may summon persons to attend, give evidence and produce specified documents or all documents of a described class; summoned persons must attend personally or by authorised agent, state the truth and produce required materials subject to the exemption for self incrimination in the Code of Civil Procedure, and such inquiries are deemed judicial proceedings attracting penal provisions for false evidence.