The Federal Communications Commission is looking into complaints by AT&T Inc. that the Google Voice phone service blocks some calls within the United States to avoid a high connection fee.
The FCC sent an inquiry to Google Inc. on Friday seeking information about the software's functionality, the number of users and the identity of its partners.
Google Voice allows users to consolidate their home, office and cellphone numbers by routing the calls through a central Google number. It records voice mail and sends written transcripts of the messages to users. The service also provides free calls within the U.S.
But AT&T alleges that Google Voice refuses to connect calls to rural communities where local telephone companies charge higher fees. AT&T did not immediately respond to e-mails seeking comment.
This isn't the first time Google's foray into telephony has drawn the attention of federal regulators. In July, the FCC began probing a dispute between AT&T, Apple and Google after Apple blocked Google Voice software from its iPhone App Store. Apple has said it has reservations about the application's interface and is still considering it for approval. AT&T said it was not involved in that decision.
In an interview Thursday, FCC Chairman Julius Genachowski said the commission was still keeping an eye on the iPhone dispute.
"We take Apple at its word," he said. "We'll continue to monitor the specific issue and to monitor the marketplace."