The confirmed death toll from Fourth of July holiday floods that ravaged the central Texas Hill Country -- including a river bank cluttered with children's summer camps -- rose to 121 as the urgent search for more than 170 people still missing entered a seventh day.

Hundreds of workers in Kerr County and other central Texas communities continue to comb through piles of muddy debris, but with no live rescues reported this week, worries have swelled that the death toll could still rise.

With US President Donald Trump preparing to visit the disaster zone Friday with First Lady Melania Trump, new questions have emerged about when the first emergency alerts reached the hundreds of people in the path of nature's fury.

Several local and state officials in recent days have deflected questions that sought to clarify Kerr County's specific actions as the disaster rapidly unfolded.

ABC News reported early Thursday that a firefighter in Ingram, upstream of Kerrville, had asked the Kerr County Sheriff's Office at 4:22 am on July 4 to alert residents of nearby Hunt of the coming flood.

The network said its affiliate KSAT obtained audio of the call, and that the first alert did not reach Kerr County's CodeRed system for a full 90 minutes.

In some cases, it said, the warning messages did not arrive until after 10:00 am, when hundreds of people had already been swept away by raging waters.

"The Guadalupe Schumacher sign is underwater on State Highway 39," the firefighter said in the dispatch audio published by ABC. "Is there any way we can send a CodeRED out to our Hunt residents, asking them to find higher ground or stay home?"

"Stand by, we have to get that approved with our supervisor," a sheriff's office dispatcher replied in the audio.

Kerr County, the tragedy's epicenter and part of an area nicknamed "Flash Flood Alley," has confirmed 97 deaths including 36 children, with 161 people still missing.

Reporters pressed area officials this week about whether the Trump government's sweeping funding cuts had weakened warning systems, and why so many people did not receive timely flood alerts.

"There's going to be an after-action" review, Kerr County Sheriff Larry Leitha said, adding "those questions need to be answered."

Leitha said "it was between 4:00 or 5:00 (am) when I got notified" of incoming emergency calls -- but he declined to address specifics of the warning system and any possible delays.

The flooding of the Guadalupe River was particularly devastating for summer camps on its banks, including Camp Mystic, where 27 girls and counselors died. Five other Mystic campers and a counselor remain missing.

Governor Gregg Abbott has scheduled a special session of the Texas Legislature, beginning July 21, with ABC reporting it will discuss improving warning systems for weather events.