The eldest of the four Indigenous children who were missing for more than five weeks in Colombia's southern jungle after a plane crash pulled her youngest sibling from the wreckage, the children's grandfather said on Monday.

The children, aged 1 through 13, survived the May 1 crash that killed their mother and two other adults and were found on Friday in Caqueta province after weeks of searching by the military and Indigenous communities.

The oldest sister, Lesly, whose courage has been hailed by authorities as key to the children's survival, pulled the youngest child, Cristin, from the plane, grandfather Narciso Mucutuy said in videos posted by the defense ministry.

"When she looked and saw that her mother was dead, she saw the feet of her littlest sister where the three dead were and she pulled her out," Mucutuy said at the Bogota military hospital where the children are being treated.

The children spent four days near the wreckage, he said, eating flour that had been onboard, before wandering from the site.

Lesly was exhausted by the time they were rescued, Mucutuy added. The children used large leaves and branches to shelter from the rain, he said, and spent time with one of the military rescue dogs sent to look for them.

The dog, Wilson, remains missing and an operation to find him is ongoing.

The children are recovering satisfactorily, the child welfare agency said, and have been able to see some family members, as well as draw and talk.

"The children are well, they are stable and following their medical treatment," said agency official Adriana Velasquez in a video posted on Twitter.

Rescuers told Colombia's public broadcaster in an interview on Sunday that the children hugged them and said they were hungry when they were found. The boy told them their mother was dead, the rescuers said.

The father of the two youngest siblings has said the children will tell their own story about the ordeal.