SEOUL—A team from U.S. hedge fund Elliott Advisors LP asked executives from Samsung C&T Corp. in April about rumors the South Korean construction and trading firm was weighing a merger with Cheil Industries Inc., the Samsung conglomerate’s de facto holding company.

Samsung C&T denied at the time that it was considering such a deal, Elliott’s lawyers said at a recent court hearing. Yet weeks later, Samsung C&T and Cheil Industries announced merger plans.

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