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A toddler is making rapid improvement after being rescued this weekend by police and firefighters from the Spanish Fork River crash that killed her mother.

Jill Sanderson, the baby girl's aunt and family spokeswoman, said Monday of 18-month-old Lily Groesbeck: "Her improvement is astounding. Right now she's watching Dora and singing 'Wheels on the Bus' with Grandpa. She is smiling and laughing for family members. We're blown away by Lily's progress and so grateful to her rescuers."

The statement appeared on the family's "GoFundMe" site.

Spanish Fork police Lt. Matt Johnson earlier Monday had confirmed that the infant's vital signs had stabilized and she appeared out of immediate danger.

Authorities believe the baby had been dangling, upside down in her car seat, for more than 12 hours after her mother, 25-year-old Lynn Jennifer Groesbeck of Springville, crashed into the side of a bridge near Arrowhead Trail and Main Street in Spanish Fork at about 10:30 p.m. Friday.

The car then plunged into the river.

Fishermen initially spotted the partially submerged, upside-down car about noon on Saturday and called 911. Responders, tipping the vehicle onto its side, found Groesbeck dead at the scene; the baby was rushed to Primary Children's Hospital in Salt Lake City.

What caused the crash remained under investigation on Monday.

"The reason for the accident hasn't yet been determined," Johnson said. "There were no signs of evasive maneuvers or skid marks. The vehicle was mechanically sound, no steering or brake-related problems."

There was no initial evidence of either drugs or alcohol being factors, though results of an autopsy and forensic blood tests were pending. Police were looking at whether Groesbeck may have fallen asleep, or experienced a medical crisis of some kind.

"At this point in time, though, we just don't know why the vehicle left the roadway," Johnson said.

The GoFundMe site for the baby and her family had exceeded $30,000 in donations by Monday afternoon.

Twitter: @remims