Google revealed that its own online video-sharing service is the subject of a copyright infringement lawsuit, adding to concerns that it may become the subject of expensive lawsuits following its acquisition of YouTube.

In Google's most recent filing with the US Securities and Exchange Commission, covering the quarter ending September 30, the search giant reports that certain entities have filed copyright infringement claims against Google Video along with several other services including Google News and Google Book Search.

The US District Court for Northern California, where Google is based, doesn't reveal any suits related to the video service but the filing could have been made in another court. It’s unclear if more than one suit has been filed regarding Google Video.

Google also conceded in the filing made that it may be subject to additional copyright infringement suits when its acquisition of YouTube closes. Adverse results from future or existing suits could require Google to pay damages or even compel it to change its business practices, Google warned.