CHIANG RAI, Thailand — Two ambulances thought to be carrying the first boys from a soccer team trapped in a Thailand cave for more than two weeks were seen leaving the area on Sunday after a squad of elite divers began a rescue operation to try and save the 12 boys and their coach.

"Two kids are out. They are currently at the field hospital near the cave," said Tossathep Boonthong, chief of Chiang Rai's health department and part of the rescue team.

"We are giving them a physical examination. They have not been moved to Chiang Rai hospital yet," Tossathep told Reuters.

Police chief confirms the first two Thai boys have been freed from the cave. Two ambulances passed me 20 minutes ago. Freedom day. — Bill Neely (@BillNeelyNBC) July 8, 2018

Chiang Rai Gov. Narongsak Osatanakorn told reporters at a briefing Sunday that the mission to save the 12 boys and their coach from Tham Luang cave began at 10 a.m. local time.

A total of 18 expert divers — 13 international and five Thai — were proceeding deep into the hillside through the waterlogged passages to the chamber where the team is located.

"One boy will be accompanied by two divers. They will come out of the cave one group at a time," Narongsak said.

A Thai army commander, Maj. Gen. Chalongchai Chaiyakam, said the ongoing rescue could take two to four days in all depending on conditions, according to the Associated Press.

CAVE RESCUE UNDERWAY: Rescuers using a “buddy diving” system where each boy is tethered to a skilled diver. Will lead them through tunnels and chambers, a 3-mile journey that takes divers 6 hours. “Our mission will be ongoing till the last kid comes out.” @NBCNews — Janis Mackey Frayer (@janisfrayer) July 8, 2018

Narongsak said that conditions inside the cave were the best they could hope for and that water levels were now so low after days of good weather and constant draining that long stretches of the passage were now walk-able.

"Today is the best day for them to come out," he said. "They really wanted to come out now as well. They are ready both mentally and physically."

An Australian medic has been inside the team's chamber and has confirmed that the boys and their coach are ready and willing to make their escape after over two weeks underground. Medical teams have been preparing for the rescue operation for three days and are ready, Narongsak said.

The boys, aged 11 to 16, and their assistant coach were found inside the cave on Monday after nine days underground. They went missing after they set out to explore the cave on June 23.

Some of the children are poor swimmers, and the journey out of the cave from the chamber they are trapped in takes even experienced Navy SEALs divers as long as five or six hours to complete.

A former Thai navy SEAL, Sanam Kunan, 38, died early Friday after losing consciousnesswhile returning from placing air tanks deep inside the caves. He could not be revived despite the attempts of a fellow diver, officials said.

Speculation that a rescue attempt was imminent was fueled when Thai authorities at 7 a.m. Sunday local time (8 p.m. Saturday ET) ordered the media, including the Thai press, to leave the area around the entrance to the cave, citing a "rescue operation."

As reporters filtered away from the site ahead of the 9 a.m. deadline, they crossed path with army medics and expert divers who were arriving.

They entered the site under brooding clouds spitting steady rain. Until Saturday evening, the torrential downpours that had been forecasted had failed to materialize, giving authorities a window to extract water from the cave and give further cave diving training to the boys. The weather broke around 9 p.m. Saturday though, with a deluge hitting the area.

Several options had been proposed — including drilling holes in the ceiling of the cave to hoist them out and keeping them supplied with sustenance inside the network of passages underneath the mountains on the border of Thailand and Myanmar, as well as scuba-diving the team through the narrow, waterlogged passages.