Comedian Kenneth Keith Kallenbach, a long-running member of Howard Stern's "Wack Pack," has died after falling ill in jail. He was 39.

Kallenbach contracted pneumonia while in custody on a charge of attempted child abduction. He died Thursday at Riddle Memorial Hospital near Media, his mother, Fay Kallenbach, said Friday.

She said her son suffered from the chronic ailment cystic fibrosis and officials at the Delaware County jail near Philadelphia had failed to properly care for him. A county official said he had been cared for promptly.

Stern first reported the news on his Sirius Satellite Radio show Thursday.

Kallenbach, whose goofball antics included attempting to blow smoke from his eyes, made dozens of appearances on Stern's show beginning in 1990. While Kallenbach appeared on the show less frequently in recent years, his name was well-known to Stern 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 Jay Leno's "Tonight" show on NBC 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 had denied any wrongdoing.

He posted bail, but was returned to custody for violating the terms of his probation. Kallenbach, who was convicted of drunken driving in 1999, pleaded guilty last May to driving without an ignition interlock device.

His mother accused the Delaware County Prison, as the jail is known, of failing to provide adequate medical care. She said her son called her a few days before his death and begged her to intervene.

"They weren't treating him properly for his disease and this is how he contracted pneumonia," Fay Kallenbach said.

Cystic fibrosis causes thick, sticky mucus to build up in the lungs and digestive system and can be fatal.

John A. Reilly Jr., acting superintendent of the prison, said he was "shocked" by the mother's allegation because she had previously thanked the jail for the care her son received.

"What more did she want us to do?" he said.

He said Kallenbach was taken to the prison hospital and placed on oxygen, then rushed to Riddle as his condition started to deteriorate.