Mass. Gen. Laws ch. 30A, § 24
(a) Whenever the attorney general has reasonable cause to believe that a person, including any public body and any other state, regional, county, municipal or other governmental official or entity, has violated the open meeting law, the attorney general may conduct an investigation to ascertain whether in fact such person has violated the open meeting law. Upon notification of an investigation, any person, public body or any other state, regional, county, municipal or other governmental official or entity who is the subject of an investigation, shall make all information necessary to conduct such investigation available to the attorney general. In the event that the person, public body or any other state, regional, county, municipal or other governmental official or entity being investigated does not voluntarily provide relevant information to the attorney general within 30 days of receiving notice of the investigation, the attorney general may:
(c) Service of any such notice may be made by:
(d) Each such notice shall: