McGregor, 29, was captured on video leaping over the Bellator cage after Ward (4-3) successfully defeated John Redmond on the Bellator prelims.
In an Instagram video posted by Bellator MMA, veteran referee Marc Goddard is seen addressing McGregor directly, before turning around to evaluate Redmond.
McGregor then followed Goddard across the cage before giving him a slight shove in the back, just before officials intervened. In the video, McGregor continued to point and yell in Goddard's direction before eventually exiting.
McGregor also slapped a Bellator staff member who was attempting to stop him from hanging on the top of the cage.
The U.S.-based Mohegan Tribe Department of Athletic Regulation oversaw the event from a regulatory standpoint and described McGregor's actions as an "assault" on Goddard.
"Mr. McGregor's conduct jeopardized the health and safety of the bout participants by delaying necessary medical attention to the fighters that were injured during the round," read a statement released Saturday by the organization. "In addition, Mr. McGregor assaulted referee Marc Goddard and a Bellator staff.
"The MTDAR has been in consultation with the upper management of the UFC regarding Mr. McGregor's inappropriate and unacceptable behavior. The MTDAR has also contacted members of the Association of Boxing Commissioners that have licensed Mr. McGregor in their jurisdictions to inform them of Mr. McGregor's behavior."
The Bellator 187 event took place Friday evening in Dublin and is scheduled to air on tape delay in the U.S. on Spike TV.
Last month, Goddard issued McGregor a formal warning during a UFC Fight Night event in Gdansk, Poland. McGregor also attended that event in support of a teammate, featherweight Artem Lobov. Goddard warned McGregor for walking around outside the cage during the fight.
It is not immediately clear whether McGregor will face any disciplinary action by the UFC or a regulatory body.
McGregor (21-3) hasn't fought in mixed martial arts in 2017. He made his massively hyped professional boxing debut against Floyd Mayweather in August. The UFC is currently in negotiations regarding McGregor's potential return in December, according to recent comments by president Dana White.