Every public utility or other person subject to investigation by the commission, shall at all times, upon request, furnish to the public utilities commission all information that it may require respecting any of the matters concerning which it is given power to investigate, and shall permit the examination of its books, records, contracts, maps, and other documents by the commission, or any of its members, or any person authorized by it in writing to make such examination, and shall furnish the commission with a complete inventory of its property in such form as the commission may direct.