The 12 Thai schoolboys rescued from a cave this week were reportedly given a “small sedative” before they embarked on a rescue mission that continues to grab international headlines.

Australian newspaper Adelaide Now reported that Dr. Richard Harris entered the cave to assess the boys’ condition before administering the sedative. Moreover, Thailand Prime Minister Prayut Chan-o-Cha confirmed the boys were given the drug “to make them not excited, not stressed,” according to the Daily Mail.

Dr. Harris was part of a comprehensive team that ensured the 12 exhausted schoolboys—ranging in age from 11 to 16—along with their soccer coach, survived the grueling two-and-a-half mile journey out the cave. Images from the successful, yet dramatic, rescue effort showed the boys lying in covered gurneys as they were being transported to the hospital.

The Mail also learned that the pumps draining water from the Tham Luang Nang Non cave in Mae Sai had failed shortly after the last boy was brought to safety.

“The favorable outcome that has been achieved is almost beyond our imagination when we first became involved in this operation,” the Austrailian-based doctor said in a statement

“We are humbled to have been able to provide our expertise and experience to assist in this international operation led by the Thai government.”

Derek Anderson, 32, a rescue specialist with the U.S. Air Force based in Okinawa, Japan, told the Mail that crews ensured the boys were “tightly packed” so divers could maintain control and adjust their air supply as needed. Anderson said one of the most crucial pieces of equipment was the positive pressure diving masks, which would expel water from the mask if one of the boys panicked.

He told the Mail, “We were extremely fortunate that the outcome was the way it was.”

[Featured image: Thai NavySEAL Facebook Page via AP]