Five ambulances were seen driving toward the cave complex on Monday afternoon, and at least one helicopter was also seen heading toward the cave entrance.
That makes for eight of the 13 people who have been trapped under increasingly risky conditions since late last month.
And although the four had been rescued, there were concerns they may have contracted an illness while in the cave, Narongsak said on Monday.
"We expect that if there is no unusual condition. the 4 boys, 1 coach, the doctor, and 3 SEALs who have been with the boys since the first day will will come out today", he told a press conference to loud cheering.
Alluding to that worry, the regional army commander offered his thanks Monday to the rain god Phra Pirun, imploring him to "keep showing us mercy".
A vehicle loaded with oxygen tanks is seen near the Tham Luang cave complex in the northern province of Chiang Rai, Thailand.
Narongsak said rescuers would meet Monday evening to plan for the next operation.
The rescue operation was launched on Sunday and four boys were brought out that day.
"This morning they said they were hungry and wanted to eat khao pad grapao", Narongsak said, referring to a Thai dish of meat fried with chili and basil and served over rice. Musk has also shared a video of the submarine being tested in a swimming pool, which as per another tweet by the founder of SpaceX, can also be used in future space missions.More news: Duke and Duchess of Sussex arrive in Ireland for tour
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Still, the four were undergoing medical checks in a hospital in the provincial capital and were not yet allowed close contact with relatives due to fear of infections.
After the various hurdles in the cave rescue of a group of children in Thailand that includes the death of one of the rescuers, Elon Musk has now offered the services of a mini submarine which was built by SpaceX engineers, which is reportedly en route to Thailand to aid with the rescue operation.
He said the extraction effort would likely resume early Monday.
"The water level is still at a satisfactory level and we have enough teams to complete the mission", Narongsak said on Monday.
Dozens of foreign divers and other experts from around the world were brought to help the rescue effort, working alongside Thai Navy SEALs.
The boys and their coach went exploring in the massive cave on June 23 after a soccer practice, and were cut off when a rainstorm flooded the cave.
Cave rescue experts have said they consider an underwater escape to be a last resort, especially with people untrained in diving. A retired Thai Navy SEAL assisting with the operation died Friday after running out of oxygen, underlining the danger of the rescue.
The daring and risky bid to rescue the boys - aged between 11 and 16 - was suspended by the mission chief late on Sunday to replenish oxygen supplies and make new preparations, which he said would take at least 10 hours.
He did not say how many boys the team hoped to bring out on Monday.
The cave complex is off-limits during the rainy season, which usually runs from May to October when downpours can quickly flood it.