A man has died after falling down a steep gorge at a popular Adelaide hiking trail.

Witnesses say the man had been trekking with a woman at Morialta National Park when he fell down a ravine near Deep View Lookout just before 12.30pm.

Witnesses who first raised the alarm say the woman approached them after the horrific incident calling for help.

“She said she just met with this man in class and she just for the first time went out with him and this thing happened,” witness Aliman Tazudin said.

The woman claimed the man jumped over a barrier along the walking trail to pick up a littered plastic bottle before he fell.

“She said her friend doesn’t like littering and because he saw a bottle over the fence so he tried to go over the fence and right after that he fell down.”

The conservation park was closed for several hours as emergency crews carried out a complex and challenging retrieval operation in difficult terrain.

“We came past one of the lookouts and saw CFS crews down there and then we saw a bunch of firetrucks and police vehicles,” parkgoer William White said.

The man died at the scene.

Police will investigate the circumstances surrounding the man’s death.