Morongo will include temperature screenings at the door and limited guest capacity, while Spotlight 29 and Tortoise Rock will implement air-purification equipment and mandatory face coverings.
Tribal officials have said that 50% of the slot chairs have been removed in order to encourage physical distancing among players.
San Manuel Casino in Highland issued a stement on Instagram that false reports were surfacing that they would reopen on June 1.
"To confirm, while we have not yet announced a re-opening date, we know it will not before the end of the month nor on June 1 as reported," the casino said.