ST. PAUL, Minn. (AP) — St. Paul authorities are again warning people to stay away from the city’s caves by the Mississippi River.

Crews were called to rescue two teenagers who were seen entering a hole leading to the caves Friday afternoon. St. Paul Assistant Fire Chief Mike Gaede says the teens emerged by themselves and were not hurt.

The Star Tribune reports the teens entered a hole the city already had planned to close Saturday.

The cave system has posed a danger for curious explorers for decades.

Gaede says the caves are not safe, and it’s illegal to be in them.

Three teenagers died from carbon-monoxide poisoning after entering the caves in 2004.

(© Copyright 2018 The Associated Press. All Rights Reserved. This material may not be published, broadcast, rewritten or redistributed.)