The hack gives G1 users a way to read data on parts of the phone that are normally walled off and could be used to install new programs, or even a new operating system, on the mobile phone. Currently, programs for the open-source Android operating system must be written in Java, rather than other popular programming languages such as C or C++.

on how to gain superuser "root" access to the phone were posted Tuesday to an Android development forum. Step-by-step instructions have also been online.

According to posters on the discussion board, the hack should be attempted only by technically sophisticated users because a misstep could render the G1 phone inoperable.

Developers were able to hack the phone thanks to a bug in the Android operating system, Google said Wednesday. "We've been notified of this issue and have developed a fix," the company said. "We're currently working with our partners to push the fix out and updating the open source code base to reflect these changes."

Android is Google's answer to Apple's iPhone. One difference, however, is that Google makes only the phone's software. The G1 itself is made by Taiwan's HTC, and Google is lining up handset makers to build other Android systems. T-Mobile is the first service provider to sell an Android phone; its G1 went on sale in late October.