Google is believed to have violated its own advertising policies by allowing illegal online pharmacies to advertise on its site without verification.

Last week, Google revealed that it had adjusted its revenue by keeping $500m for a probe being investigated by the Department of Justice.

Google had said in a filing with the the Securities and Exchange Commission (SEC), "In May 2011, in connection with a potential resolution of an investigation by the United States Department of Justice into the use of Google advertising by certain advertisers, we accrued $500 million for the three month period ended March 31, 2011."

Now, the search engine company is close to a settlement with regulators following an investigation, The Wall Street Journal has reported.

The investigation, which involves the Food and Drug Administration (FDA), the Justice Department and the United States attorney for Rhode Island, is about whether Google displayed ads from online pharmacies that sell fake drugs or drugs that need a prescription from a licensed medical practitioner without verification.

Google had it mandatory for online companies to get their ads vetted by verification firms. However, it has come to light that the practice was stopped in early 2010.

Google has not commented on the matter so far. The FDA and the United States attorney’s office in Rhode Island have also not spoken about the case.