Google took a surprise $500 million charge in its first quarter to cover potential charges related to resolving an investigation by the Department of Justice.

The revelation came in the company's quarterly filing with the Securities and Exchange Commission. It was first reported by GeekWire.

In the filing, Google wrote that it took the charge as "a potential resolution of an investigation by the United States Department of Justice into the use of Google advertising by certain advertisers." The company said it took the charge this month, but accrued it against earnings in the period that ended March 31.

Google was not specific in its filing regarding the investigation, and a company spokesman declined comment because it's a legal matter. A Justice Department spokesman declined comment as well.

There have been a handful of antitrust claims against the company related to advertising. Last year, for example, Columbus, Ohio-based MyTriggers, which runs an online shopping comparison search site, accused Google of manipulating search results to penalize it, a claim Google has denied.

As large as the sum is, Google's balance sheet can clearly handle it. "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," Google wrote in the filing.

The news comes on the first day of Google's giant developer conference, Google I/O.

Updated at 5:55 p.m. with Justice Department declining to comment.