Santa Ana, Calif. -- In follow-up to its prior announcement that it would explore strategic alternatives, including a potential sale or merger, real estate services and investment firm Grubb & Ellis Co. said Tuesday that is exclusivity period with Colony Capital LLC, which had expressed interest in exploring a strategic transaction with Grubb & Ellis, ended on May 29. Grubb & Ellis said that, while it will continue its discussions with Colony, it will engage in additional discussions with other parties.