By Marcus Leach

Google have revealed that their advertising system is to be investigated by the US Justice Department.

The focus of the investigation, for which Google has set aside $500 million to settle any potential charges, will centre around how the search giants automated advertising system treats several unnamed advertisers.

Further to the US Justice Department inquiry there is a separate study to be carried out by the European Commission after Google announced advertising revenues of over $8 billion for the first quarter of 2011.

Google announced that the US Justice Department investigation in a regulatory filing to the US financial watchdog, the Securities and Exchange Commission.

Given the fact Google has had to set aside $500 million in case charges are brought against them, their profits for the opening quarter of 2011 have been revised, dropping to $1.8 billion from $2.3 billion.

"Although we cannot predict the ultimate outcome of this matter, we believe it will not have a material adverse effect on our business, consolidated financial position, results of operations, or cash flows," a Google statement read.