JOHN YANG: Good evening.

I'm John Yang.

Tonight, the desperate search for the missing after deadly flash floods in Texas has become a race against time.

The official death toll has climbed to at least 70 and 11 girls from a Christian camp are still unaccounted for.

With each passing hour, the chances of finding survivors dwindles.

Ali Rogin has our report.

ALI ROGIN (voice-over): In parts of Central Texas, the floodwaters have receded, but grief hangs in the air as the search for the missing girls from Camp Mystic widens.

Inside their deserted cabins, muddied cots and overturned tables lie scattered.

Saturday evening, Texas Governor Greg Abbott visited the campsite, vowing to work around the clock to find the girls and bring them home safely.

In nearby Kerrville, downed trees and destroyed homes litter neighborhoods along the Guadalupe River.

On Friday, the river surged past 29ft before the gauge failed, the second highest level ever recorded.

Ground crews gathered to sift through debris and search for survivors today, while rescue teams and helicopters airlifted as many people as they could.

For many, their only escape route was to climb onto their rooftops.

Meanwhile, locals like Arnaldo Pena are pitching in to help where they can.

ARNALDO PENA, Resident: My dog is like a German shepherd, so I want to see if we can find someone, you know, help out some families.

ALI ROGIN (voice-over): The National Weather Service first detected floods in the region late Thursday night.

TONIA FUCCI, Flood Survivor: The RV park right at the end of my Granny's road that were completely flooded.

ALI ROGIN (voice-over): But some people in the area said the alerts didn't reach them in time.

TONIA FUCCI: No warnings at all.

They came hours later, which was the most devastating part.

We got the warnings on our phones hours later.

Hours later.

ALI ROGIN (voice-over): Kerrville city officials were pressed today on why early warnings from the Texas Division of Emergency Management didn't reach the area camps and force evacuations.

DALTON RICE, KERRVILLE CITY MANAGER: That is a great question, but again, we want to make sure that we continue to focus.

We still have 11 missing children that we want to get reunited with our families.

JONATHAN PORTER, AccuWeather Chief Meteorologist: This is the flash flood capital of the United States.

It's infamous for having many life threatening and tragic flash floods over the decades.

ALI ROGIN (voice-over): AccuWeather Chief Meteorologist Jonathan Porter said it comes down to a matter of local communication.

JONATHAN PORTER: There were several hours of advance notice before the peak of the inundation reached, for example, the Hunt area across Texas as a result of a flash flood warning that was issued by the national weather service at 1:14 in the morning Central Time.

The question is going to have to be how did entities receive those warnings, the local officials and also the people that were responsible for the safety.

ALI ROGIN (voice-over): Prayers for those Texas communities poured in from around the world at the Vatican and in central Texas, where people came together to mourn the lives lost and hope for more survivors.

For PBS News Weekend, I'm Ali Rogin.