A frantic search for survivors is under way in central Texas after flash floods killed at least 32 people, including 14 children.

Many were asleep when the Guadalupe River rose more than 26 ft (8m) in less than an hour in the early hours of Friday.

Officials in Kerr County have said 27 children are missing from a Christian youth camp located along the river. Some 850 people were rescued.

Weather forecasts suggest that more rain and, potentially, more flooding could be on the horizon for the area.

Among the areas most severely hit by the floods were mobile homes, summer camps and camping sites where many had gathered for 4 July holiday celebrations.

At a press conference on Saturday afternoon, Texas Governor Greg Abbott said he had signed an expanded disaster declaration to boost search efforts.

He said officials would be relentless in ensuring they locate “every single person who’s been a victim of this event”, adding that “we will stop when job is completed”.

It remains a search and rescue mission, officials said, not a recovery effort.

They said rescuers were going up and down the Guadalupe River to try to find people who may have been swept away by the floods.

Much of the rescue has focused on a large all-girls Christian summer camp called Camp Mystic.

The camp, where 27 remain missing, is on the banks of the Guadalupe River near Hunt, Texas.

Texas Lieutenant Governor Dan Patrick told the BBC’s Radio 4 PM programme that of the 27 children missing from Camp Mystic “many of these girls are younger girls under the age of 12”.

He also said that many more people were likely to remain unaccounted for across the region, because some were visiting for the holiday weekend.

In an email to parents of the roughly 750 campers, Camp Mystic said that if they haven’t been contacted directly, their child is considered missing.

Some of the families have already stated publicly that their children were among those who were found dead.

US President Donald Trump has said his administration is working closely with local authorities to respond to the emergency.

Homeland Security Secretary Kristi Noem said the president was “devastated” by the loss of life and promised full federal support.

Noem joined Governor Abbott at Saturday afternoon’s press conference and said the federal government would soon be deploying the Coast Guard to help search efforts.

Elsewhere in central Texas, in Travis County, officials say another two people have died and 10 are missing because of the flooding.

Forecasters have warned that central Texas may see more flooding this weekend.

The National Weather Service (NWS) said the area could see 2 to 5in (5cm to 12cm) of rain on Saturday.

Up to 10in of rain was possible in some areas that are still reeling from Friday’s deluge.