Authorities warned citizens to stay out of St. Paul's river bluff cave system after eight people were rescued Tuesday morning from a cave at Crosby Farm Regional Park.
No one was injured during the rescue about 150 feet up a steep, rocky hillside across from Watergate Marina.
"I can't stress how dangerous this is," said Sgt. Mike Ernster, a police spokesman. "The situation can change dramatically. … I would urge everybody to stay out of the bluff line."
Police and fire officials said it's unclear what the group was doing inside the cave, which also serves as a storm drainage system.
Six people between the ages of 15 and 17 were taken into police custody and will be released to their parents, Ernster said.
An 18-year-old man was expected to be booked into the county jail and faces possible gross misdemeanor trespassing charges.
Police and fire officials said an 18-year-old woman was taken to the hospital for a "situation" unrelated to Tuesday's incident.
The group intentionally ignored rescuers who called out to them, but cooperated once they were found "huddled in a corner," said Assistant Fire Chief Michael Gaede.