An 18-month-old girl has been found strapped in a car seat upside down about 14 hours her mother’s fatal crash into a frigid Utah river.

Lily Groesbeck’s condition has been upgraded from critical to stable but critical at a Salt Lake City hospital. Her 25-year-old mother, Lynn Groesbeck, was found dead in the car.

“She is doing remarkably well considering the circumstance. The doctors have been hopeful so far,” Lily’s aunt, Jill Sanderson, told local station KSL-TV.

• ‘They’re kids, not killers’: Dutton
• Train slams into car at crossing 

A fisherman found the child and woman Saturday. Photo: ABC

“We would like to express our appreciation to the Spanish Fork rescue team for saving the baby’s life.”

A fisherman discovered the car on its top about 12:30pm on Saturday in the Spanish Fork River about 80 kilometres south of Salt Lake City, police Lieutenant Matt Johnson said.

The temperature dropped close to freezing overnight while Lily was trapped.

She was found hanging upside down above the water flowing through the car, Johnson told the Deseret News newspaper. Her mother was found in the driver’s seat.

Investigators believe the wreck occurred about 10:30pm on Friday, when a resident near the scene reported hearing something. The resident was unable to find anything out of the ordinary when checking the area.

The car struck a cement barrier on the bridge and careened into the river, investigators said. Police are unsure why the car left the road.

Relatives told police that Groesbeck was heading home when the crash occurred.

Three police officers and four firefighters who entered the river were released after hospital treatment for hypothermia.