(CNN) Former Trump campaign chairman Paul Manafort has accused federal prosecutors of carrying out an illegal search of his property, according to a court filing late Friday night.

Manafort asked the judge overseeing his case in DC to suppress evidence FBI agents collected from his Alexandria, Virginia, storage unit last May, which was only 10 days after Robert Mueller was appointed as special counsel to look into possible collusion between the Trump campaign and Russia.

Manafort has pleaded not guilty to charges related to his foreign lobbying work and other financial decisions before he became Trump campaign chair. Even so, prosecutors have made it clear they are still pursuing other angles of the investigation that involve Manafort, and have fought his team at every step of the case.

The aggressive investigation into Manafort included the sweep last year of the storage unit that took mere minutes, and that Manafort now alleges may have violated his Fourth Amendment rights.

Manafort's attorneys say an investigator looked around the unit with the help of a former low-level employee of Manafort's who wasn't authorized to give them that permission. A day later, investigators used a warrant to collect the business documents within it. Both the initial visit and the raid violated Manafort's constitutional protections, his attorneys argued Friday.

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