IOWA CITY, Iowa —Rescue crews tunneled through two walls at the University of Iowa Hospitals and Clinics to save a worker who fell into a large ventilation shaft.

The Iowa City Press-Citizen says the man was performing work on the hospital roof when fell down the 25-foot deep shaft about 7:50 a.m. Friday.

Iowa City Fire Department Batallion Chief Brian Platz says the shaft was about two stories deep.

Nearby ambulance workers were able to lower a ladder down and start treatment before rescue crews cut through walls to reach him about 30 minutes later.

Platz says the man was conscious and alert during the ordeal.