More than 160 people remain unaccounted for after devastating floods in Texas, Governor Greg Abbott announced, marking a dramatic increase in the number of missing from a disaster that has already killed 109 people.

Four days after flash floods ravaged several Texas counties, some striking while residents slept, hopes of finding survivors by Tuesday have dwindled – and Abbott warned that the number of missing people could still rise further.

“Just in the Kerr County area alone, there are 161 people who are known to be missing,” he told reporters on Tuesday as the grim search continued.

“There very likely could be more added to that list,” he added, explaining that the figure comes from individuals reported missing by friends, relatives and neighbours.

Kerr County, located in central Texas’s “Flash Flood Alley,” suffered the most catastrophic impact, with at least 94 confirmed deaths.

This toll includes at least 27 girls and counsellors who were staying at a youth summer camp along the Guadalupe River when it overflowed early on Friday morning as the Fourth of July holiday began.

Powerful floodwaters surged through the camp, demolishing cabins while hundreds slept.

As of Tuesday evening, five campers and one counsellor remained missing, according to Abbott, along with another child not associated with the camp.

“There’s nothing more important in our hearts and minds than the people of this community, especially those who are still lost,” Abbott said.

Throughout the rest of the state, at least 15 additional deaths have been recorded, the governor added.

Ben Baker with the Texas game wardens explained that search and rescue operations using helicopters, drones and dogs face tremendous obstacles due to water and mud.

“When we’re trying to make these recoveries, these large piles can be very obstructive, and to get in deep into these piles, it’s very hazardous,” Baker said.

“It’s extremely treacherous, time-consuming. It’s dirty work, the water is still there.”