TMZ has obtained the official crash report issued by Colombian authorities in this case ... and it goes into great detail about how exactly this aircraft they were all on went down, and more importantly -- how these children could've possibly made it out relatively unscathed.

Check out these never-before-seen photos of the aftermath showing the wreckage ... as well as the diagrams experts crafted to demonstrate how this tragedy quite likely unfolded.

For starters ... you can see that this plane lost its engine as it was falling out of the sky and that the mechanical piece itself ended up landing far away from the actual crash site.

Here's what else you can see ... the plane was totally crushed, but more so on the front -- as it appears to have nosedived straight into the jungle after flying too low and seemingly clipping the tree line. After that, the plane went plummeting straight into the ground.

The reason this is relevant to the children's survival ... their position in seating onboard. Investigators found that the kids were all sitting near the back of the plane -- whereas the adults, including their late mother, were upfront ... which explains how she died.

What doesn't make sense -- and what can only be described as a true miracle -- is the fact that the 1-year-old baby in the group (who also survived) was discovered to have been sitting in his mother's lap during the crash. And yet ... the infant somehow escaped death.

As we reported ... these kids not only lived through the plane crash -- which is incredible in and of itself -- but they went on to survive an extra 40 days in the jungle on their own.

When they were finally discovered by a search party ... the reunion was absolutely joyous. And while it proved to be a happy moment -- you could absolutely tell these little ones had been through a rigorous journey. Their full tale has yet to be told ... but it's still fascinating.