Section 14. Investigators and examiners appointed under section twelve F of chapter twenty-five, with respect to the enforcement of the laws relating to commercial motor vehicles, including laws and regulations relating to safety on public ways, shall have and exercise throughout the commonwealth all the powers of constables, except the service of civil processes, and of police officers, and they may serve all processes issued by the courts or the department or the director of the transportation division. Any officer authorized to make arrests may arrest without warrant and keep in custody for not more than twenty-four hours, unless Sunday intervenes, any person operating a commercial motor vehicle on any public way who does not have in his possession a license to operate motor vehicles granted to him by the registrar of motor vehicles of this commonwealth, and who violates any statute, by-law, ordinance or regulation relating to the operation or control of commercial motor vehicles and the weights and dimensions thereof and at or before the expiration of said period of time, such person shall be brought before a magistrate or court and proceeded against according to law. An investigator or examiner appointed under chapter twenty-five may arrest without warrant, keep in custody for a like period of time, bring before a magistrate and proceed against in like manner, any person operating a commercial motor vehicle while under the influence of liquors, irrespective of his possession of such license.