Special counsel Robert Mueller is adding more prosecutors and FBI agents to his investigation into Russian interference in the 2016 elections, a sign that officials say could indicate that the year-long investigation continues to expand.

[Also read: Byron York: One year down, and it’s still Mueller time]

The addition of Justices Department resources such as attorneys and FBI agents, could be a sign that Mueller is laying the groundwork to hand off some parts of the investigation, current and former U.S. officials told Bloomberg .

Mueller’s probe has already been under attack for how long it has been going on for and how much money has been spent.

After a little over a year, the special counsel’s team spent $7.7 million on the investigation into Russian interference. Mueller also has a team of 17 federal prosecutors that are already working on the investigation.

President Trump has repeatedly called the investigation a “witch hunt” and has maintained that there was no collusion between his campaign and the Russian government.