Buzzfeed reporter Zoe Tillman notes that special counsel Robert Mueller has filed the paperwork to add four new prosecutors. All of them are to be assigned to prosecuting the case against Internet Research Agency, the Russian operation that both disseminated propaganda during the 2016 election through social media posts, false fronts for nonexistent organizations, and intentionally provocative ads. Among the prosecutors being added is Heather Alpino, who has worked on a number of cases involving international agents—including the prosecution of a Turkish national for arms smuggling and of Iranian hackers involved in credit fraud.

The addition of four additional lawyers represents a significant staffing up for this area of the investigation. It may suggest that additional information has been acquired, requiring more hands to deal with growing complexity. It may also suggest that some of those currently dealing with the case are needed for other areas of the investigation and those coming on board will act as backfill.

In either case, requiring additional attorneys would seem to indicate that the investigation into connections between the Trump campaign staff and foreign agents is continuing to expand.

In a separate action, Robert Mueller has filed a motion to prevent former Trump campaign manager Paul Manafort from challenging the authority of the special counsel’s office during his upcoming trial. Manafort’s attorney’s filed a series of pre-trial motions suggesting that the special counsel’s office had gone beyond its writ in looking into crimes not directly connected to the 2016 campaign, and in directing FBI raids on Manafort’s home and office. Manafort lost those challenges, as well as a “swing for the fences” attempt to have the whole idea of a special counsel declared unconstitutional.

The process of fighting off those challenges demanded both time and attention from the Mueller investigation, and also resulted in the public filing of documents that revealed significant facts about the information for the first time—including that Deputy Attorney General Rod Rosenstein had expanded Mueller’s authority, including giving him specific instructions to look into Manafort’s activities in Europe.