Sounds like a local mine is on the verge of reopening. What might be inside?
Once the event starts, player can enter a normally inaccessible abandoned mine. Next, they have to repair three Auto-Miner robots inside the mine and protect them from enemy attacks to receive claim tokens. The faster they are repaired, the bigger the token haul that can be redeemed at the terminal just outside the mine (100 tokens are required for the biggest reward).
Furthermore, the mine is absolutely chock-full of containers stocked with very useful high-level crafting materials. Of course, the mine will eventually start collapsing again and players will have a limited window of opportunity to get out and avoid dropping all the materials they gathered.