Four police officers rushing to an overturned car in an icy Utah river say they all heard the same thing: a mysterious female voice calling out “Help,” from inside the vehicle.

But the driver of the car was dead and her 18-month-old daughter, while still alive, couldn’t have been the speaker.

It was a mystery that continues to haunt the officers – and may never be explained.

Officer Jared Warner of the Spanish Fork Police Department was one of the first who came to the rescue of tiny Lily Groesback, who was strapped in a seat in the back of her mother’s car, which was precariously hanging upside down in 40-degree water.

“We’ve gotten together and just talk about it and all four of us can swear that we heard somebody inside the car saying, ‘Help,’” Warner told Deseret News.

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But when they flipped over the midsized car, they discovered a 25-year-old woman dead in the front seat and Lily unconscious in her car seat.

“The only people in there were the deceased mother and the child,” Officer Bryan Dewitt told the paper.

Officer Tyler Beddoes said they can't explain it, but have no doubt they heard it.

"It wasn't just something that was just in our heads. To me it was plain as day cause I remember hearing a voice," Beddoes told the Deseret News. "I think it was Dewitt who said, 'We're trying. We're trying our best to get in there.' How do you explain that? I don't know," he said.

Nobody knows exactly how the infant survived hanging upside down for nearly 14 hours in her car seat with no food or water. As she dangled, icy water rushed just below her head through broken car windows as the vehicle sat perched on the bank and rocks. The temperatures were near freezing throughout the night and through the morning.

"It's heartbreaking. Was she crying most the night?" said Beddoes, a 30-year-old father of two. "It's a miracle. . . She was needed for sure elsewhere."

Police believe the accident occurred when the baby's mother, 25-year-old Lynn Groesbeck, struck a cement barrier on a bridge and careened into the river late Friday in Spanish Fork, about 50 miles south of Salt Lake City.

She was driving to her home in Springville after visiting her parents in Salem, Spanish Fork police Lt. Matt Johnson said. Investigators don't know what caused the crash, he said. There were no skid marks or signs of mechanical failures in the car.

Police don't suspect drugs or alcohol as a factor but are awaiting toxicology test results. Maybe Lynn Groesbeck was tired or distracted, Johnson said, adding authorities weren't ruling anything out.

Beddoes said the family has thanked him and the other officers for helping to save little Lily. As he recalls the events of those chaotic moments, on a frigid but sunny day, Beddoes still can't believe the girl survived — and still can't make sense of that undeniable voice coming from the car.

"We all got together and we all heard the same type of thing," Beddoes said. "We just can't grasp what we were hearing."

The Associated Press contributed to this report