The U.S. Federal Trade Commission has requested additional information from Caesars Entertainment and Fertitta Entertainment as they advance their merger valued at about $5.7 billion.

The companies said they would cooperate and provide the supplemental materials and written information regulators have sought.

In May, Tilman Fertitta reached an agreement to acquire Caesars Entertainment at $31 per share, with about $11.9 billion of Caesars’ debt to be assumed. When the transaction closes, more than 50 Caesars resorts would join Fertitta’s business empire.

Separately, Caesars disclosed in an SEC filing that board members Jesse Lynn and Ted Papapostolou will resign, and the Icahn Group relinquished its right to nominate replacement directors.