A car slipped of a jack and crushed a woman working underneath the vehicle late Tuesday afternoon on the Northside.
Police were called to the 500 block of Hardeeville Court about 5 p.m.
Investigators said 47-year-old Patricia Rempe was pinned under the car for more than an hour before being discovered.
She was rushed to Shands Jacksonville Medical Center with life-threatening injuries. She remained in critical condition Wednesday.