Four Indigenous children who survived 40 days in the Colombian Amazon have been released from a military hospital after a monthlong stay, authorities said Friday, adding that the siblings were doing "very well."

Lesly (13), Soleiny (9), Tien Noriel (5) and baby Cristin (1) were the only survivors after the small plane they were flying in crashed in the jungle.

All three adults on board, including their mother, died.

They were rescued on June 9, and taken to a military hospital in Bogota to recover.

The four were discharged on Thursday night, said the Colombian Family Welfare Institute, which will temporarily take custody of the children.

"They have recovered... weight, they are actually very well," institute director Astrid Caceres told reporters.

The children show no physical effects from the 40 days they spent wandering the Amazon, she said, and even little Cristin is "completely recovered in terms of physical development."

The children appeared emaciated in photos taken shortly after they were found, and in the hospital they were given food typical of the Huitoto Indigenous group to which they belong, such as cassava flour.

Relatives say the children managed to survived thanks to Lesly's deep knowledge of survival in the jungle, with its many inherent dangers -- including snakes, predatory animals and armed criminal groups.

It took nearly 200 military and Indigenous rescuers with search dogs to track them down.

The Colombian Family Welfare Institute said it will maintain custody of the children for at least six months, as authorities investigate their family background.

After their rescue, a custody battle ensued between the maternal grandparents and the father of the two younger children.

The siblings will live with other children in a shelter, whose location was not disclosed. Caceres said the children will be in a rural area where they will feel "comfortable."