ABC has announced that singer Jewel Kilcher and Access Hollywood co-anchor Nancy O'Dell have both withdrawn from Dancing with the Stars' upcoming eighth season after sustaining serious injuries while training for the reality dance competition.

"Like most sports, dancing can be a demanding, physical activity. Each participant of Dancing with the Stars warrants in contract that they are physically fit enough to participate in the competition. We love and appreciate Nancy and Jewel's competitive spirit, drive and desire to perform their best," Dancing with the Stars executive producer Conrad Green said. "Though we share in their disappointment that they can no longer continue, their physical well-being takes precedent above all else. We thank them both for giving it their all and wish them a quick and full recovery."

Jewel had revealed she'd been diagnosed with knee tendinitis in both of her knees last week but had later announced that she was responding to treatment and expected to "be good to go" by this week.  However, further testing determined that her problems were much more severe than tendinitis and she had actually fractured the tibia in both of her legs.

"When the doctors told me my injuries were so severe that I couldn't walk, let alone compete, I was devastated that I couldn't continue the show," said Jewel, who added that her husband champion bull rider Ty Warren would still be competing in the competition."I have every intention of being at Dancing with the Stars this season supporting my husband, Ty, and his partner, Chelsie [Hightower]. I hope to be back on the show in the future."

O'Dell's departure from the show comes as more of a surprise than Jewel's. According to the network, the TV anchor suffered by torn meniscus in two places in her knee that will require surgery.

"Beyond disappointment doesn't even being to describe how I feel about not being able to continue on Dancing with the Stars," O'Dell said. "It has been one of my favorite shows since Season One! But I have torn the meniscus in my knee in two places, which requires surgery. Dancing with the Stars was a great experience. I'll miss working with my partner, Tony Dovolani, and all the other wonderful people on the amazing production that is Dancing with the Stars."

As usual, ABC isn't revealing how Dancing with the Stars will deal with the withdrawals of the injured celebrities, stating only that "additional changes to the cast" will be announced during the show's live eighth-season premiere on Monday, March 9 at 8PM ET/PT.

In addition, the network is still not confirming recent reports that The Girls Next Door star Holly Madison will be joining the cast as a replacement celebrity.