Rescuers in Thailand retrieved four of the 12 boys who have been trapped with their soccer coach in a cave for two weeks in the first phase of an operation that could take days.

Chiang Rai provincial acting Gov. Narongsak Osatanakorn said the four healthiest boys were taken from the cave first. The rescued children have been taken to the hospital, though their condition was not immediately clear.

The entire operation to get all 13 out of the cave could last two to four days, depending on weather and water conditions, army Maj. Gen. Chalongchai Chaiyakam said. Praying for their safety.