Heavy metal idols Black Sabbath were idle for a second concert along the OzzFest tour due to frontman Ozzy Osbourne's mystery illness.

Sabbath dropped out of its headlining spot on the multi-band, multi-stage metal fest last Wednesday in New Jersey and group remained MIA for Sunday's stop in Noblesville, Ind., Yahoo's Launch Radio Networks reported Monday.

OzzFest organizers have been hush-hush about the nature Osbourne's ailment. The only official statement on the tour's Web site was posted last Wednesday saying Sabbath was sitting out the Jersey show due to an "illness in the camp."

Iron Maiden stepped in as the main stage headliner. The tour's next stop is Tuesday in Columbus, Ohio.