In Texas, frantic search and rescue efforts continue, with Governor Greg Abbott vowing emergency crews “will not stop until every missing person is accounted for”. Abbott added that it was very likely more missing would be added to the list in the coming days, and urged people to report anyone they think was unaccounted for.

General Thomas Suelzer from the Texas National Guard said search efforts were using Chinook and Black Hawk helicopters with rescue hoists. He said there were 13 Black Hawk helicopters helping in the search effort, including four that arrived from Arkansas. Authorities have also been using reaper drones.

Responders from various agencies are working together on rescue efforts. They include agents from border patrol, the FBI and the National Guard.

More than 250 responders from various agencies have been assigned to the Kerrville area alone to help with search and rescue.

One of those rescue volunteers, named Tim, told the BBC he had never seen any destruction at this scale before.

“I’ve done the floods down in East Texas and Southeast Texas, and hurricanes, and this is a nightmare,” he said.

Another rescue volunteer, named Justin, compared the effort to “trying to find a single hay in a haystack”.

“There’s a wide trail of destruction for miles, and there’s not enough cadaver dogs to go through all of it,” he told the BBC. “It’s hard to access a lot of it with heavy machinery. Guys are trying to pick at it with tools and hands, and they’re not even putting a dent in it – not for lack of effort.”

Questions have been raised about whether authorities provided adequate flood warnings before the disaster, and why people were not evacuated earlier.

Experts say there were a number of factors that contributed to the tragedy in Texas, including the extreme weather, the location of the holiday homes and timing.

Abbott, who had spent part of the day surveying the flood zone, said authorities had issued a storm warning and knew about a possible flash flood, but “didn’t know the magnitude of the storm”.

No-one knew it would lead to a “30-foot high tsunami wall of water”, he said.

But after the children fell ill, officers had to search for the supplies which had been hidden.

The paint was clearly marked as inedible, the statement said.

One parent told the BBC that he was worried about the long-term effects of lead poisoning on his son’s liver and digestive system.

Mr Liu took his child to hospital in Xi’an for testing last week after other parents raised the alarm. His son now needs 10 days of treatment and medication.

Chinese state media aired footage which it said was from CCTV cameras in the kitchen which showed staff adding paint pigment to the food.

Investigators found that the red date cake and the corn sausage rolls had lead levels of 1052mg/kg and 1340mg/kg respectively which both exceed the national food safety standard limit of 0.5mg/kg.

The principal of the privately-run kindergarten and seven others, including its main investor, will now be investigated on suspicion of producing toxic and harmful food.

It is not known how long the paint has been used in the food, but several parents told Chinese state media that their children have been complaining of stomach and leg pain and a lack of appetite since March.

An investigation was launched after they raised their concerns with the local authorities.

The mayor of Tianshui, Liu Lijiang, said the incident exposed shortcomings and loopholes in public food safety supervision and the city would draw lessons from the event.