The third phase of the high-risk rescue operation for the boys and their coach trapped in a cave in Thailand began Tuesday. Four boys were rescued Sunday and an additional four emerged Monday.

The head of the rescue mission says their plan is based on bringing four people out each day. That’s partly because it takes about 20 hours to re-set all of the oxygen tanks they use inside the cave during the rescues. So it is not clear if all five of those remaining inside will get out on Tuesday.

Rescuers have been taking the strongest boys out first. It may seem counterintuitive, but the reasoning for that was that officials want the boys who have the best chance of surviving to get through the escape route first.

The boys, ages 11-16, and their 25-year-old coach became stranded when they went exploring inside after a practice game. Monsoon flooding blocked off their escape and prevented rescuers from finding them for almost 10 days.

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