29.6. An inspector may, upon written application, require of a bailiff, within five days or within such additional reasonable time as he may fix, that he produce, free of charge and by registered or certified mail, a copy of the books, registers, accounts or other documents referred to in section 26, if he has reasonable grounds to believe that an offence against this Act or the regulations thereunder has been committed and if he is of the opinion that such books, registers, accounts or other documents are related to the offence.