Section 17. The court may at any time direct an examination of the title, or the making of a plan, of any land included in the petition, or such investigation relating to the description or title of any of it as seems useful or desirable for its better division or sale. If it appears from the report of a title examiner or from any other source that there are necessary parties, as defined in section six, who were not made parties to the petition, and have not appeared, the court shall, before proceeding further, cause the petitioner to amend his petition by making such persons parties, and to give notice to them in the manner provided in section eight. The court may also cause notice to be given to any encumbrancer whose interest may be disclosed by the examination or otherwise. If it appears at any stage of the proceedings that the land is improperly described, the court may, before proceeding further, require the petitioner to amend his petition by inserting a correct description.