Alabama investigators are reviewing traffic camera footage for clues to what happened to Carlee Russell, the 25-year-old nursing student who called 911 Thursday night to report a toddler walking alone on an interstate highway and then disappeared when she stopped to see if she could help.

The video shows Russell driving slowly along the shoulder of Interstate 459, hazard lights flashing before she stops. Her mother, Talitha Russell, said she was on the phone with her brother’s girlfriend, telling her about the child, AL.com reported.

“My son’s girlfriend heard her asking the child, ‘Are you OK?’ She never heard the child say anything but then she heard our daughter scream,’’ Talitha Russell said. “All you hear on her phone is background noise from the interstate.”

“Her car door was open,” Talitha said. “They found her phone on the ground, along with her wig and her hat…Her purse was still in the car. Her Apple watch was in her purse and her Air Pods as well.”

Hoover Police Chief Nick Derzis said investigators have looked at the video, but “it’s not the greatest.” He said investigators are working to get it enhanced for a better view.

Russell called 911 at about 9:34 p.m., after she’d stopped to pick up dinner for herself and her mother. She was on the phone with her brother’s girlfriend two minutes later. She said the child she saw looked to be 3 or 4 years old.

Police, dispatched on the original call, arrived to find Russell’s car still running but no sign of her or a toddler.

Dervis said that finding Russell is “our top priority.”

A reward of up to $25,000 has been offered for information.

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[Featured image: Carlee Russell/Hoover Police Department]