Robert Mueller may not be through with Rick Gates, a deputy Trump campaign aide and one of the four people who have been charged as part of the special counsel probe into Russian meddling in the 2016 election.

In a court appearance Monday in Manhattan, Gates’ attorney Walter Mack said that federal prosecutors have told him that more charges, called superseding indictments, may be coming.

“We don’t know what the government is going to do,” Mack said in court, referring to both Gates’ case and a white-collar case in New York involving one of Gates’ business partners. “I mean, in both cases we’ve been told that there may be a superseder. We don’t know what’s happening.”

Mueller charged President Donald Trump’s former campaign chairman Paul Manafort and his deputy, Gates, on October 30 with 12 alleged crimes related to money laundering and foreign lobbying violations. Both have pleaded not guilty. The charges against Manafort and Gates are unrelated to the Trump campaign, though it’s possible Mueller could add additional federal charges.

Mack represents both Gates in DC and his business partner in New York. Neither is a witness or co-defendant in the other’s case, federal prosecutors say, but attorneys from Mueller’s special counsel investigation have raised the possibility that a conflict of interest could arise between the two men and their attorney.

The indictments came almost six months after Mueller assumed the federal investigation into Russian collusion, yet so far the charges have not directly related to Manafort and Gates’ work for the Trump campaign or to Russian foreign policy.

This week, lawyers working for Mueller revealed that Manafort was ghostwriting an op-ed about Ukraine with a Russian as recently as last Thursday. It’s unclear how the investigators found this new information, as the op-ed was never published. The prosecutors have submitted it to the court under seal.

The ghostwriting revelation puts a proposed bail deal for Manafort in question. He and Gates are both currently under house arrest and GPS monitoring and subject to $10 million and $5 million unsecured bond, respectively. The federal prosecutors argue they’re both flight risks.

Manafort’s lawyers are expected to respond to the op-ed accusation by Thursday, and both Manafort and Gates are scheduled to appear in court December 11.

It’s not unusual for federal prosecutors to charge defendants in white-collar cases once part of their investigation is complete, then bring additional charges later on. Typically, a second round of charges can come if the prosecutors had more work to do in certain aspects of the investigation or if they’re attempting to persuade a defendant toward a plea agreement or cooperation in a broader investigation.

Two targets in Mueller’s investigation, Michael Flynn and George Papadopoulos, have already pleaded guilty to charges of lying to investigators.

The other case that Gates’ lawyer is working on involves three defendants who allegedly took part in a scheme to defraud feature film and documentary movie investors. Mack’s client, Steven Brown, has pleaded not guilty and is scheduled for a trial in March.

Gates was a partner in one of the companies caught up in those charges. Gates is not accused of wrongdoing in the New York case.

The New York judge verified in a hearing Monday that Brown understood the possibility of a conflict of interest and chose to keep Mack as his attorney.

Mack declined to comment, as did a spokesperson with the special counsel’s office.

The judge in Gates’ case in DC has ordered the lawyers involved not to make comments that could influence public perception of Gates and Manafort, and not to share documents outside of the official court proceedings. Mack mentioned those restrictions in his court appearance in New York Monday, calling them and the prosecutors’ ability to bring up new information about Gates, such as his connection to Brown, “unfair.”