Narongsak Osottanakorn told reporters the operation started at 10.08am with 19 divers assigned to extract four young footballers and their 25-year-old assistant coach, Ekkapon Chantawong.
He said they got an earlier start than on the previous two rescue days, Sunday and Monday, and felt confident in the experience gained.
Despite rain overnight, the water level inside the cave was similar to that of Monday, Narongsak said.
Also to be brought out on Tuesday were the physician and three Navy SEAL divers who had stayed with the remaining footballers on the Noen Nom Sao ledge where they’d been found stranded.
Flash flooding trapped the group in the cave on June 23, sparking a multinational rescue mission that had to overcome numerous difficulties, including strong currents of murky water submerging sections of the cave.
A pair of British cave divers found them on July 2, alive but exhausted on a sandy ledge above the water level.
Their state of health posed a further challenge to the rescue effort, as did the surging water levels and rough subterranean terrain.
Narongsak decided on Sunday to launch the rescue operation after being assured the water had receded and the boys’ health was improving thanks to nourishment given them by the SEALs team.
Narongsak said two of the boys evacuated on Sunday emerged with lung infections, but their condition was improving with doses of antibiotics.
The eight boys undergoing treatment at Chiang Rai Prachanukroh Hospital were in general good health, both physically and mentally, he said.
One of them has low body temperature after spending days in the cold cave but is also improving.