Officials now say it's a suspected carbon dioxide leak coming from a malfunctioning soda machine.
On the scene along with the Pulaski County Sheriff's Office are crews with the Arkansas Department of Emergency Management.
It's not believed that anyone needed to be taken to the hospital.
It's not yet know when the restaurant will be reopened.
As of this posting, people were still evacuated from the building and standing outside.
Original story (11:57 a.m. Friday):
Staff and customers have been sickened this morning at a south Pulaski County McDonald's restaurant.
The situation prompted an evacuation of the building at Arch Street and Pratt Road.
The Pulaski County Sheriff's Office tells KARK 4 that officials on the scene expect a carbon monoxide problem.
We'll have more details as they become available.