Section 3. The mayor of a city or the selectmen of a town, having knowledge that a strike or lockout is seriously threatened or has actually occurred therein, shall at once give notice to the board. Notice may be given by the employer or by the employees concerned in the controversy, strike or lockout. When the board has knowledge that a strike or lockout, which involves an employer and his present or former employees, is seriously threatened or has actually occurred, the board shall, as soon as may be, communicate with such employer and employees and endeavor by mediation to obtain an amicable settlement, or endeavor to persuade them to submit the controversy to a local board of conciliation and arbitration established under section nine or to the board. If a settlement is not agreed upon and the parties refuse to submit the matter in dispute to arbitration, the board shall investigate the cause of such controversy and ascertain which of the parties thereto is mainly responsible or blameworthy for the existence or continuance of the same, and shall, unless a settlement of the controversy is reached, make and publish a report finding such cause and assigning such responsibility or blame. The board may employ agents to assist in said investigation. It shall, upon the request of the governor, investigate and report upon a controversy if in his opinion it seriously affects or threatens seriously to affect the public welfare. The board shall have the same powers for the foregoing purpose as are given to it by sections five to eight, inclusive. The board shall by publication or otherwise inform employers and employees of their duty to give notice to the board before resorting to a strike or lockout and of the provisions of this chapter affecting the rights of employers and employees relative to industrial disputes.