LIMA, Pa. — Comedian Kenneth Keith Kallenbach, a long-running member of Howard Stern's "Wack Pack," died of complications from cystic fibrosis, a medical examiner ruled Friday.

He died April 24 at age 39 at a hospital near Philadelphia after falling ill in the county jail. Kallenbach was being held on a charge of attempted child abduction. He had denied any wrongdoing.

An autopsy revealed the cause of death was attributable to cystic fibrosis — a potentially fatal condition in which thick, sticky mucus builds up in the lungs and digestive system.

Kallenbach's mother had accused the Delaware County Prison of failing to provide her son with adequate medical care.

Kallenbach, whose goofball antics included attempting to blow smoke from his eyes, made dozens of appearances on Stern's radio show beginning in 1990. While Kallenbach appeared on the show less frequently in recent years, his name was well-known to Stern's fans.

Stern once likened him to MTV's Beavis and Butt-head and wrote in his 1993 book "Private Parts" that Kallenbach was the "ultimate airhead."

More recently, Kallenbach of Boothwyn, Pa., appeared in commercials for ESPN's "Monday Night Football" and Stride chewing gum. He also appeared on the "Tonight" show and had uncredited parts in HBO's "Sex and the City" and the Tom Cruise film "Jerry Maguire."

Kallenbach was arrested in Upper Chichester Township, Pa., in mid-March on a charge of attempted child abduction after he was accused of trying to pull a girl into his car.

He posted bail, but was returned to custody for violating the terms of his probation.