The NRL labelled Latrell Mitchell and Josh Addo-Carr's alleged breaking of social-distancing rules as "unacceptable" and "disappointing".
South Sydney Rabbitohs' Mitchell and Melbourne Storm's Addo-Carr were pictured breaking social-distancing rules, The Daily Telegraph reported, and police confirmed on Monday they were investigating.
Amid the coronavirus pandemic, the reported incident was a blow to the NRL as it plans to resume its season on May 28.
In a statement on Monday, the NRL slammed Mitchell and Addo-Carr and said it would support action against the pair.
"Our players are role models and we expect them to lead by example during this pandemic," it said.
"On face value, the image in today's media is both disappointing and an unacceptable breach of health orders.
"The NRL will be speaking to the players involved to seek further information and we will ensure the players provide any assistance authorities require.
"We are embarking on a significant education program to ensure our players understand what is acceptable behaviour ahead of the resumption of training.
"When training resumes our players and officials must comply with biosecurity protocols that go further than current government restrictions.
"As a group, our players have taken government health orders very seriously and have helped educate the community.
"On face value, today's matter is unacceptable and we support the government in any action they believe necessary."
Australia has seen more than 6,700 confirmed cases of coronavirus, including 83 deaths.