The second day of rescue operations at the cave site in northern Thailand has ended after four more boys were brought out of the flooded cave system Monday.

Eight boys have now been freed in total, while four remain inside the flooded Tham Luang Nang Non cave complex with their coach. They now face their 17th night trapped on a ledge four kilometers (2.5 miles) inside the cave system.

Their rescued teammates are being treated in quarantine at Chiang Rai Prachanukroh hospital. Former Chiang Rai governor and rescue mission commander Narongsak Osotthanakorn said Sunday night that doctors were monitoring the rescued boys for any illnesses they may have picked up in the cave and supervising efforts to build up their strength after they spent more than two weeks with little food and no natural light.

Thai Prime Minister Prayut Chan-o-cha was visiting the hospital Monday evening after speaking with the families, who are all still gathered near the cave entrance.

Speaking Monday evening, Osotthanakorn said that those rescued Monday were in better condition than those freed the previous day, adding that all the boys rescued are well.

The rescue workers, who are now resting, need at least 20 hours to prepare for the third operation, Osotthanakorn said, but timings could change depending on weather and water levels. Monday's rescue was carried out four to five hours ahead of schedule due to favorable conditions, he said.

Officials said late Sunday that the operation had been paused to allow oxygen tanks depleted during the first phase to be refilled. It is unclear whether that was also a determining factor in suspending operations Monday. (CNN)