(a) If, before the expiration of the term for which the grand jury was impaneled, the foreperson or a majority of the grand jurors declares in open court that the grand jury’s investigation of the matters before the grand jury cannot be concluded before the expiration of the term, the judge of the district court in which the grand jury was impaneled may, by an order entered on the minutes of the court, extend, from time to time, the period during which the grand jury serves, for the purpose of concluding the investigation of matters then before the grand jury.
(b) The extended period during which the grand jury serves under Subsection (a) may not exceed a total of 90 days after the expiration date of the term for which the grand jury was impaneled.

(c) All indictments pertaining to the investigation for which the extension was granted returned by the grand jury during the extended period are as valid as if returned before the expiration of the term.