Rescue experts have worked through the night in an effort to save eight Swiss holiday-makers, who are trapped in a water-filled cave in France.
About 300 rescue workers were called to the site in Goumois, on the French-Swiss border, in an effort to save the five men and three women.
At midnight, officials said they still had no information on their fate. One official said: "It's a fight against time and water."
The last contact with the eight, who are aged between 25 and 30, was on Wednesday night.
Rescuers said their greatest chance for survival rested on whether they had reached a place within the cave's twisting passageways where they could breathe.
The eight have two days' worth of drinking water.
Divers have been prevented from going deep into the cave because it is so narrow.
Swiss television reports that thanks to an end to the heavy rain and hours of pumping, the water level in the cave had fallen dramatically. This could quicken the rescue operation, as swirling, muddy waters have hindered its progress.
Seven of the people are student social workers from a Zurich college and one is a teacher. Television reports said they had undertaken the tour to help develop their ability to face challenges in their careers.
The cave is not deep, but wends its way over some 415 meters.
PA