MAE SAI, Thailand -- With more rain coming, 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.''

Rescue workers pump water out of the cave in Thailand where the team is trapped. Getty Images

He said he asked Thai navy SEALs in charge of extraction plans to estimate what sort of a risk would be involved to take the team members out and "what kind of readiness we can have today and decide if we can take that chance.'' He said earlier that not all 13 may be extracted at the same time, depending on their condition. He said that the boys have been practicing wearing diving masks and breathing, but he doesn't believe they have attempted any practice dives.

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.

They are hoping that an upgraded draining effort can lower the water level in an area where it is still at the ceiling or just about. The idea is to get some headroom so the boys would not be reliant on scuba apparatus for a long stretch and could keep their heads above water.

The boys, ages 11 to 16, and their 25-year-old coach disappeared after they went exploring in the Tham Luang Nang Non cave in the northern province after a soccer game June 23.

Authorities said the boys, who appeared skinny but in good health in several videos released by the Thai navy, were being looked after by seven members of the Thai SEALs, including medics, who were staying with them inside the cave. They were mostly in stable condition and have received high-protein drinks.

In all of the videos, the boys appeared in good spirits. In the most recent video, a navy SEAL is shown treating minor cuts on the feet and legs of the boys with antibiotic ointment. Several of the boys are seen smiling as they interact with the navy SEAL, who cracks jokes.

Seeing the boys has boosted the mood of their family members, and officials are working to install an internet cable to the cave so that parents can talk to their children.

Kian Kamluang, whose 16-year-old son, Pornchai, is in the cave, said she had thought there would a 50 percent chance that her son would be found.

"It's like he has been given a new life,'' she said, adding that she'll never let her son go into a cave or near water again.

While efforts to pump out floodwaters are continuing, some Thai officials have indicated that heavy rains forecast for this weekend could force them to decide whether the boys should swim and dive out using the same complicated route of narrow passageways through which their rescuers entered.

Authorities said they were still exploring other options, such as scouring the mountainside for other ways into the cave and finding faster ways to pump water from the cave.

Cave rescue experts have said it could be safest to simply supply the boys where they are for now, and wait for the water to go down. That could take months, however, given that Thailand's rainy season typically lasts through October.

Divers are wary of taking out the boys through the dark and dangerous waters still in the cave, especially since they are untrained.

"We are talking kilometers of transport under the water with zero visibility,'' said Claus Rasmusen, a certified cave-diving instructor based in Thailand who has been helping the Thai SEAL team with logistics. "It's difficult.''

He said it was awkward, but possible, to teach them minimal skills.

"Nobody will teach anyone a full cave course, but trying to get them comfortable with masks, with the breathing, [is] completely different,'' he said. "Creating an environment that can make them safely get away -- that's feasible.''