Several apps began rolling out on the App Store this morning with HealthKit support for Apple’s new Health app, but it seems issues on Apple’s side have forced HealthKit-compatible apps to be completely removed from the App Store the morning of iOS 8’s (and Apple’s Health app’s) release.

Apps affected include workout app Carrot Fit, calorie counting app MyFitnessPal, and major health app WebMD among others. Each app that has been pulled from availability on the App Store previously introduced full support for iOS 8’s HealthKit feature, which Apple encouraged developers of such apps to have ready for iOS 8 launch day earlier this year at WWDC. Federico Viticci shared on Twitter that Apple has contacted two HealthKit app developers about the situation.

Another large maker of health related apps postponed its planned launch of Health integration at the last minute today due to delays from Apple, according to sources. It’s unclear if the apps will return in time for iOS 8’s launch scheduled for later this morning, but completely removing these apps from the App Store is not a good sign of something to expect on launch day.

Update: It looks like Apple is working on a fix for HealthKit and that Health- integrated apps might not be ready for today’s launch, according to tweets from developer of the Carrot Fit app Brian Mueller:

Update 2: Apple has commented on the issue and says the bug that caused HealthKit to be held back is expected to be resolved by the end of the month.