Three teenagers were rescued by police after becoming lost in a national park in Adelaide’s south.

Police were alerted to the missing trio, aged 15, 17 and 19 years old, just after 7pm on Sunday.

The police helicopter responded after reports the teens were lost on the Sundews Track within Onkaparinga River National Park. 

A green sign on a post which says Sunderws Trk

Police searched for teens lost on the Sundews Track within the national park. (ABC News: Isabella Carbone)

Police said all three were located “deep within the park” about 7:20pm.

Southern District patrols then hiked through the area on foot, traversing steep terrain and knee-deep water before finding the teenagers and escorting them to safety.

No one was injured, police said.

Police said the rescue was a reminder that darkness can fall quickly during shorter winter days.

They also advised hikers to carry appropriate safety equipment, take sufficient food and water, stick to marked trails and let someone know the planned route and expected return time.

Police said anyone lost should stay where they are and contact Triple Zero (000) for assistance.

A map outlining the walking paths at Onkaparinga River National Park

Police hiked through the Onkaparinga Rivers National Park in search of the three teenagers.  (ABC News: Isabella Carbone)