WASHINGTON, Aug. 1 (UPI) -- Apple and AT&T have been targeted in an antitrust probe for allegedly denying iPhone owners access to an application made by Google, federal officials say.

The Federal Communications Commission demanded in letters Friday that Apple and AT&T explain why Google's voice application has been shut out of the iPhone's applications store, a sign that the Obama administration is intent on cracking down on perceived anti-competitive activity in the high-tech and telecommunications sectors, The Washington Post reported.

The letters from FCC Chairman Julius Genachowski asserted that the agency "has a mission to foster a competitive wireless marketplace, protect and empower consumers, and promote innovation and investment. Recent news reports raise questions about practices in the mobile marketplace."

The Post said Apple declined to comment on the letters, while the newspaper said it could not reach AT&T for comment. A spokesperson for Google said the Internet giant had submitted its voice application to the Apple App store six weeks ago but alleged that Apple did not approve it.

The FCC is also probing other aspects of the wireless industry, such as exclusive agreements between handset makers and phone carriers, the Post said.

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