The attorney general of the US state of Texas has opened an inquiry into whether internet giant Google manipulates search results.

Google disclosed the antitrust probe in a blog post late last week following a report by technology website SearchEngineLand.com on the investigation by the Texas authorities.

"We recognise that as Google grows, we're going to face more questions about how our business works," Google's deputy general counsel Don Harrison said.

"As Search Engine Land first reported, we've recently been approached by Texas Attorney General Greg Abbott's office, which is conducting an antitrust review of Google," Harrison said.

"We look forward to answering their questions because we're confident that Google operates in the best interests of our users," he said.