Another investor in SunCoke Energy Partners has sued to stop a planned investor vote later this month on a proposed merger with its general partner and majority owner, unless company officials turn over information the board allegedly withheld.

The complaint, filed Friday in Delaware federal court, claimed investors were missing important financial information necessary to decide whether to approve the deal, in which SunCoke would purchase all publicly traded units of SunCoke Energy Partners that it did not already own, in exchange for SunCoke stock.