Four Utah police officers said they heard a voice distinctly call out for help when they found a vehicle submerged upside-down in a river.

But when they flipped the vehicle over, they discovered there was nobody in the car who was able to speak, reported Deseret News.

“The only people in there were the deceased mother and the child,” said Officer Bryan DeWitt, of Spanish Fork police.

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Lynn Jennifer “Jenny” Groesbeck was pronounced dead at the scene, but her 18-month-old daughter, Lily, was still alive after remaining strapped upside-down in a car seat for up to 14 hours.

The toddler was listed Sunday in critical but stable condition at a nearby hospital.

Investigators said the 25-year-old Groesbeck was driving home about 10:30 p.m. Friday from visiting her parents in Salem when her car went off the road and crashed into the water.

A fisherman spotted the vehicle about 12:30 p.m. Saturday and called police to report the crash.

“We were down on the car and a distinct voice says, ‘Help me, help me,'” DeWitt said.

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“It wasn’t just something that was just in our heads,” said Officer Tyler Beddoes, who insists the voice did not sound like a child. “To me it was plain as day because I remember hearing a voice. 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,” Beddoes added.

They were upset to discover the unconscious child, believing she might be dead, but they were encouraged when they saw her eyes flutter as they cut the straps on the car seat.

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Several firefighters were treated for hypothermia after jumping into the river, which ran 10 feet deep in some places, to rescue the child.

“We’ve gotten together and just talking about it, and all four of us can swear that we heard somebody inside the car saying, ‘Help,'” said Officer Jared Warren. “We’re not exactly sure where that voice came from.”

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Watch this video report posted online by KHON-TV: