Apple has released Beta 2 versions of its iOS 4.1 and iOS software development kit 4.1 to developers.
The releases have only been made available for members of its $99-a-year developer program.
Apple has said that the releases, both of which are available for download from the Apple Developer Centre, are pre-release versions and classified under the Apple Confidential information non-disclosure agreement.
The company has said that iOS SDK 4.1 Beta 2 will be able to run on Mac OS X 10.6.4, and has advised developers that the iOS 4.1 Beta 2 should be only installed on systems dedicated to software testing.
Apple has also specified that iOS4.1 Beta 2 will be only able to run on the Phone 3G, iPhone 3GS, iPhone 4, as well as second and third-generation iPod Touch devices.
Developers have been asked to first look over the release notes before installing the SDK on their systems.
Apple is yet to announce when the software will be made available for public download.