In this image made from video taken Sunday, June 24, 2018, rescue teams gather at the entrance of a deep cave where a group of boys went missing in Chang Rai, northern Thailand. (TPBS via AP)
Rescuers in northern Thailand are in a race against time on Monday to locate 12 boys and their soccer coach after a heavy rainstorm flooded the entrance to a popular cave they visited over the weekend.
The boys, aged 11 to 15, are believed to have entered the Tham Luang Nang Non cave in Chiang Rai province late Saturday afternoon with their 25-year-old coach, according to Sky News.
Heavy rain flooded a stream to the entrance of the cave, trapping the group, according to officials. A mother reported that her son did not return from soccer practice that day, setting off the search.
"We are still searching right now," Chote Narin, an officer at Mae Sai district police station, told The Associated Press on Monday. "We've found traces but no people yet.
Rescue teams gather at the entrance of a deep cave where a group of boys went missing in Chiang Rai, northern Thailand, Monday, June 25, 2018. (Thai News Pix via AP)
Narin said that footprints and handprints discovered in the cave are believed to belong to the group of boys.
Navy SEAL divers were trying to reach a large chamber deep inside the cave complex where officials thought the students might be.
The chamber is about 2.5 miles from the entrance of the cave, which is thought to be about 4-5 miles long and cut into a mountainside in far northern Thailand near the border with Myanmar.
In this photo taken Saturday, June 23, 2018, stalactites hang at the entrance to a large cave where a group of boys went missing in Chang Rai, northern Thailand. (Chiang Rai Public Relations Department via AP)
Police Chief Komsan Saardluan told Sky News that parts of the cave get flooded to a height of up to 16 feet during the rainy season, which runs from June to October.
Thai television showed footage of bikes and backpacks left at the cave entrance as soldiers swarmed the area.
In this image made from video taken Sunday, June 24, 2018, bicycles left from a group of boys who went missing stand parked outside a deep cave in Chang Rai, northern Thailand. (TPBS via AP)
Kamolchai Kotcha, an official at the forest park where the cave is located, told the AP that attempts to reach the chamber had failed as the passage is extremely small, "flooded and covered with sand and mud."
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"Right now, our family is hoping that the children trapped inside will have formed a group and are safe and waiting for officials to go in and save them in time. That's what I'm hoping," Noppadol Kantawong, the father of one of the missing boys, told Thai PBS television on Sunday.
According to Kamolchai, tourists trapped in the cave by past floods have been rescued after the water receded a few days later.
Bicycles left by a group of missing boys lean against a railing at the entrance of a deep cave in Chiang Rai, northern Thailand, Monday, June 25, 2018. (Thai News Pix via AP)
In "The Caves of Northern Thailand," an online guidebook last updated this year, the cave is described as only explorable from November to June due to flooding.
It says the cave has an "impressive entrance chamber" that is about 260 feet long and leads to an easy walk along "spacious passageways" that last for about a half a mile.
The Associated Press contributed to this report.