Officials from the National Park Management Board described their attempt as potentially deadly.
Travelling into Son Doong Cave without professional equipment or proper guidance is dangerous and might lead to life-threatening situations, said Le Thanh Tinh, Director of the national park.
The group reportedly admitted that they were using navigation devices to attempt to access Hang En Cave and Son Doong Cave, and agreed to pay an undisclosed administrative fine and proceeded to visit other approved destinations in the park.
Son Doong opened to tourists in 2013, four years after members of the British Cave Research Association concluded their initial exploration and declared it the world’s largest cave. The 5km system contains at least 150 individual caves, a dense subterranean jungle and several underground rivers.