The Attorney General of the State of North Carolina shall have power, and it shall be his duty, to investigate, from time to time, the affairs of all corporations or persons doing business in this State, which are or may be embraced within the meaning of the statutes of this State defining and denouncing trusts and combinations against trade and commerce, or which he shall be of opinion are so embraced, and all other corporations or persons in North Carolina doing business in violation of law; and all other corporations of every character engaged in this State in the business of transporting property or passengers, or transmitting messages, and all other public service corporations of any kind or nature whatever which are doing business in the State for hire.