Nine 18-year-old hikers have been killed and one is missing after a flash flood swept them away in Nahal Tzafit, southern Israel.
Israeli media said they belonged to a group of around 25, who were members of a pre-army preparatory programme.
Some 15 other hikers were rescued, two of them reportedly suffering from hypothermia.
They are being treated at Soroka Medical Center in Be'er Sheva, Israeli newspaper Haaretz reports.
The group had been walking close to the Tzafit stream, near the Dead Sea, when the flood struck.
"We were unable to escape the current and were swept away by the river," one of the rescued students told Channel 10 news.
Of the nine teenagers who died, eight were women, according to Haaretz.
Army rescue helicopters and the fire brigade's diving unit are searching for the missing hiker, believed to be a young woman.
"We are now in a race against time to find the missing before it gets dark," said Eli Bin, director general of the Magen David Adom medical rescue service.
Police spokesperson Meirav Lapidot said authorities were "preparing for a long night of search and rescue operations".
"Some have been rescued and some are still out there. We will keep going until we find them all," she said earlier, when several of the students were being treated as missing.
Weather agencies had issued flood warnings for the area after unusually heavy rainfall on Wednesday.
Israel's President Reuven Rivlin said security and rescue forces would be supported, and called on the public to follow instructions given by the police.
"Our prayers and thoughts are with our brothers, our children, and our loved ones who are in trouble. We are closely following the updates from the south and send a warm embrace to the worried families," he said.
"We are all praying for better news," said Prime Minister Benjamin Netanyahu.