Despite initial signs that Google would be able to complete the ITA acquisition without too much fuss, it now looks like the company is going to have to wait as the US Department of Justice is apparently investigating whether the acquisition raises anti-trust concerns.

While Google doesn't currently compete in the online travel market, there are worries that its entry will prove detrimental to existing players.

According to the Wall Street Journal, citing anonymous sources close to the authorities, the DoJ is now inquiring competitors trying to determine if Google could use its size and position in search to unfairly dominate the market.

ITA serves as a middleman for many travel-related sites and services including the websites of several airlines, flight-information and comparison sites and others.

More importantly, it also powers Bing's travel search vertical. Google doesn't currently offer dedicated travel information and directs this type of searches to appropriate websites.

The DoJ is worried that Google may block access to the ITA data to competitors so it's trying to find out if there are alternatives to ITA which Microsoft and others could use, if the case may be.

The second issue is whether Google will use its position in search to direct users to its own travel services rather than to those of competitors.

While Google may very well build its own flight search engine and direct related searches to it, it is well within its right to do so.

The Google search engine, while very important to a lot of people, is not a public service and the search results rankings are Google's to determine.

Google is under increasing scrutiny as it gets bigger and enters new markets. Last year's AdMob acquisition was on hold for several months as the DoJ investigated the deal before finally approving it.