BOGOTÁ, May 18 — Four Indigenous children missing for more than two weeks after a plane crash in the Colombian Amazon have been found alive, President Gustavo Petro said Wednesday, declaring "joy for the country”.

Petro shared the news on Twitter, saying the children were discovered after "arduous search efforts” by the military.

Authorities had deployed more than 100 soldiers with sniffer dogs to search for the minors who were traveling in an airplane that crashed in the Amazon on May 1, killing three adults.

Rescuers believe the four children, aged 13, nine, four and an 11-month-old baby, have been wandering through the jungle in the southern Caqueta department since the crash.

Earlier Wednesday, the armed forces said that search efforts intensified after rescuers came across a "shelter built in an improvised way with sticks and branches”, leading them to believe there were survivors.

In photographs released by the armed forces, scissors and a hair tie could be seen among branches on the jungle floor.

Previously, a baby’s drinking bottle and a half-eaten piece of fruit had been found.

On Monday and Tuesday, soldiers found the bodies of the pilot and two adults who had been flying from a jungle location to San Jose del Guaviare, one of the main cities in Colombia’s Amazon rainforest.

One of the dead passengers, Ranoque Mucutuy, was the mother of the four children, who are from the Huitoto ethnicity.

Giant trees that can grow up to 40 metres tall, wild animals and heavy rainfall made the "Operation Hope” search difficult.

Three helicopters have been used to help, one of which blasted out a recorded message from the children’s grandmother in the Huitoto language telling them to stop moving through the jungle.

Authorities have not indicated what caused the plane crash.

The pilot had reported problems with the engine just minutes before the airplane disappeared from radars, the Colombian disaster response body said.

It is a region with few roads that is also difficult to access by river, so airplane transport is common. — AFP