Google Inc is about to receive the civil equivalent of a subpoena from the U.S. Federal Trade Commission as part of a probe into the giant Web company's Internet search business, the Wall Street Journal reported on Thursday, citing people familiar with the matter.

Separately, the Financial Times on Friday reported that attorneys-general in California, New York and Ohio have also started antitrust investigations into Google.

The states that have recently joined the inquiries into Google are still at an early stage in their deliberations, people familiar with their thinking told the Financial Times.

The company, which dominates U.S. and global markets for search advertising, has been accused by competitors of favoring its own services over rivals in its search results.

Google, the world's No. 1 search engine, and the FTC declined to comment on the Journal report.

Google was not immediately available for comment on the Financial Times report. The attorney general of California declined comment while the attorneys general of New York and Ohio were not immediately available for comment.

The FTC plans to send the civil investigative demand with a request for more information, the civil equivalent of a subpoena, within five days, according to the report.

U.S. antitrust regulators have been concerned about Google's dominance of the Web search industry, and it has been under investigation by the European Commission since last November.

Complaints has been filed with regulators on both sides of the Atlantic, many from Google rivals who specialize in vertical searches like price comparison websites, which are widely seen as a threat to Google's position as a key gateway to online information.

The distraction that comes from a federal investigation should not be underestimated, Colin Gillis of BGC Partners said, noting that one of Google's best options to grow -- by moving into adjacent markets -- was being hampered by antitrust probes.

Gillis noted that the real cost of the FTC investigation was not financial. The issue comes down to management distraction, that's a real cost, he said.

Google has been in a stock slump. Share prices began the year a touch above $600, but are now below $500. Google was trading at $476.60 on Thursday, down just more than 2 percent.

Google has weathered other antitrust setbacks. The company walked away from a search deal with Yahoo! Inc in 2008 when the Justice Department signaled it was prepared to challenge it.

A New York judge has said that a deal Google had made with publishers and authors to create a massive digital library was illegal, partially because it effectively gave Google the rights to books that are in copyright but whose authors cannot be found.

(Reporting by Bill Rigby, Diane Bartz and Abhishek Takle in Bangalore; Editing by John Wallace and Maureen Bavdek)