Four Spanish Fork police officers all said they heard it.
"We've gotten together and just talkin' about it, and all four of us can swear that we heard somebody inside the car saying, 'Help,'" officer Jared Warner recalled Sunday.
But when they flipped the vehicle resting on its hood in the Spanish Fork River onto its side Saturday, they discovered there was no one inside able to speak.
"The only people in there were the deceased mother and the child," said officer Bryan Dewitt.
"We're not exactly sure where that voice came from," Warner told the Deseret News.