Two young women have been airlifted to Auckland City Hospital after an incident on a school tramping trip in the Waitakere Ranges.

Rescue services rushed to Muir Track west of Auckland after a tramping group of 22 students and three teachers set off an emergency beacon early this evening.

The Westpac Rescue Helicopter was sent to help the group, near Karekare beach, just south of Piha.

They eventually airlifted two 16-year-old girls to hospital. It is understood they needed for treatment of hypothermia.

The group were off the track, police said.

Ambulance and search and rescue staff are with the rest of the party and are assessing options for the group to walk out tonight.

In a separate incident in the same area, a 17-year-old girl suffered knee and hip injuries while tramping in a six-strong group on the Twin Peak Track near Huia.

The girl is unable to walk out and emergency services are on their way.

That group is well provisioned and in contact with emergency services.