The U.S. Department of Justice is looking at the Google-Yahoo (NSDQ: YHOO) two-week ad test, according to Reuters. The wire service says it has been told by a source that authorities have initiated an investigation over concerns the test could violate antitrust law. 

SEE ALSO: Yahoo’s Google Test Positive; Moving Closer To An Alternative?

The test, announced early this month, was limited to two weeks, U.S. searches of Yahoo.com and just 3 percent of search queries. 

Update: The companies have confirmed communications with the DOJ. A Google (NSDQ: GOOG) spokesman told Reuters: “We informed the Justice Department before we launched this test and we have been responsive to their questions about it.” Separately, a Yahoo spokesman said the company has pro-actively kept the DOJ in the loop.