A bug in Apple’s HealthKit platform has delayed the launch of several third-party health and fitness apps, casting a shadow on yesterday's release of the company's much-awaited iOS 8.

"We discovered a bug that prevents us from making HealthKit apps available on iOS 8 today", an Apple spokesperson said, adding that the company is working quickly to have the bug fixed in a software update and have HealthKit apps available by the end of the month.

Several developers of fitness-tracking apps including MyFitnessPal, Carrot Fit, and more were expecting their applications to be available for iOS 8 at Apple's App Store, but that didn't happen.

"The MyFitnessPal app, which supports integration with Apple's HealthKit, was temporarily removed from the Apple Store this morning to address some minor issues", MyFitnessPal said in a statement.

Carrot Fit developer Brian Mueller was apprised of the situation in a call from Apple. “The rep couldn’t clarify what was wrong", he said, adding that users of the app who had already downloaded the update were able to use the HealthKit features without any problem.

Health information service provider WebMD also confirmed that the new version of its app, which was designed to take advantage of the HealthKit platform, was removed from the app store, although it said that it's hoping to see the previous version (v 5.2) back in the store on a temporary basis.

HealthKit is a platform designed to let third-party fitness apps talk to Apple's new Health app, which will track a user’s heart rate, calories burned, and other fitness-related metrics. All the information is stored in a centralized location that, the company says, no one can access without the user's permission.