Google (NASDAQ:GOOG) (NASDAQ:GOOGL) has been accused by the U.S. Department of Justice of destroying internal communications the agency needs for its antitrust case over the tech giant’s search business.

In a court filing obtained by Reuters, the DOJ said that Google (GOOG) (GOOGL) « empowered, and even encouraged » employees to turn their history off in written communications, which resulted in them being automatically destroyed after 24 hours.

« Google even trained employees that ‘off the record’ chats, also known as Google Hangouts or instant messages, are ‘[b]etter than sending [an] email’ and ‘not retained by Google as emails are,’ the DOJ said in its filing.

« Google’s daily destruction of written records prejudiced the United States by depriving it of a rich source of candid discussions between Google’s executives, including likely trial witnesses, » the agency asserted.

The DOJ has asked the District of Columbia court and U.S. District Judge Amit Mehta to hold a hearing on the matter and discuss appropriate sanctions.

A Google spokesman told the news outlet that it « strongly » refutes the allegations.

« Our teams have conscientiously worked for years to respond to inquiries and litigation, » a spokesperson said, adding that the company has produced more than 4M documents in this case.

If the court finds Google (GOOG) (GOOGL) violated rules, it can restrict what it is allowed to argue at trial or a potential monetary fine.

The case is set to be heard in court in September.

Earlier this week, it was reported that the Justice Dept. is pressing forward with another case against Google (GOOG) (GOOGL), this time over its Google Maps application.