Thai rescuers are racing against time to pump out water from a flooded cave before they can extract 12 boys and their soccer coach with minimum risk, officials said Thursday.

A firefighter who has been working on draining the water said that levels in parts of a passage leading to the chamber where the boys and the coach were found on Monday after being missing for 10 days was still flooded all the way to the ceiling, making diving the only way out.

“What we worry most is the weather,” Chiang Rai provincial Gov. Narongsak Osatanakorn told reporters. “We can’t risk having the flood back into the cave.”

Officials have said they prefer to get the boys out as soon as possible because heavy rain is expected to start by Saturday, which almost surely will raise water levels again in the cave, making passage in some areas even more difficult, if not impossible. This will no doubt one day be made into a movie.