Troopers say a Nissan Pathfinder with four people inside struck the guardrail about 4:30 a.m. and overturned.
The driver, Jacob Thomas Lin-Justiniano, and front-seat passenger, Ronnie Keoni Powell, both 22 of Jacksonville, were critically injured and transported to Orange Park Medical Center.
Passengers Fiona Ann Castor, 21, of Middleburg, was transported to Baptist South Medical Center, and Qiante Jackson, 23, of Jacksonville, was taken to Orange Park Medical Center -- both with serious injuries, according to the FHP.
According to Doug Lipscomb, branch manager of Blue Bell Creameries, shortly after the SUV flipped, a Blue Bell Ice Cream truck was traveling in the middle lane when another vehicle in the left lane swerved in front of it.
The truck driver, David Alvarez, 23, swerved to avoid hitting that vehicle, then had to take immediate action again to avoid the overturned SUV.
Troopers say none of the occupants of the vehicle were wearing seat belts.
The accident had the two inside lanes of I-295 southbound shut down while police and fire rescue responded to the crash.
The scene was finally clear and all lanes reopened about 8:15 a.m.