SECTION 1A. Completion of investigations by grand juries; notice; order

Upon a written notice by the attorney general or any district attorney made to any justice of the superior court that public necessity requires further time by a grand jury to complete an investigation then in progress, the court may order such grand jury to continue to serve until said investigation has been completed and shall take up no new matter.

This section shall not be construed to prevent the issuance of writs of venire facias authorized by section one for impanelling a grand jury whose duty shall include all business not then before the grand jury continued under authorization of this section.