Former New Jersey Gov. Chris Christie has not been keeping quiet lately when it comes to Robert Mueller's investigation into possible Russian interference in the 2016 presidential election.

During a recent appearance at the University of Chicago, Christie said President Trump hadn't been doing himself any favors in bringing the special counsel's probe to an end.

"I've told him many times that there's no way to make an investigation like this shorter, but there's lot of ways to make it longer and he's executed on a number of those ways to make it longer," Christie said.

The former governor, who left office in January, also called Mueller an "honest" and "hard working guy" and said "you can't argue the investigation hasn't been effective so far," The Hill reported.

The Mueller investigation, which hit the one-year mark last week, has resulted in charges against 19 people and three businesses, and five people have pleaded guilty.

In a separate interview on Showtime's "The Circus," Christie also discussed the investigation with host John Heilemann. In that conversation, Christie also touched on Bridgegate — a scandal that Christie was not charged in but did little to help his own campaign for the presidency — calling the attention he received "very analogous" to the Trump-Russia probe.

"You're being followed everywhere, and screamed at and yelled at with questions, charges and all this," he said. "And then the issue of continuing to run the government, and not only keeping yourself focused but keeping everybody else focused on the mission, which is not dealing with your crisis. It's hard, it's really hard."

Christie called his experience "incredibly frustrating."

Over the weekend, the president once again took to Twitter to comment on investigation, calling it a "witch hunt" and demanding the Department of Justice look into whether the FBI "infiltrated or surveilled" his campaign.

"If anyone did infiltrate or surveil participants in a presidential campaign for inappropriate purposes, we need to know about it and take appropriate action," Deputy Attorney General Rod J. Rosenstein said in a statement, according to the Washington Post.