Manafort, 68, and his longtime deputy Gates, 45, have pleaded not guilty and remain under home detention while details are worked out for their release on secured bonds of $10 million and nearly $5 million, respectively.
They were indicted Oct. 30 in connection with Manafort's secret lobbying for a Russia-friendly political party in Ukraine, in the first publicly disclosed criminal charges in Mueller's investigation of possible Russian influence in U.S. political affairs.
Separately, former Trump national security adviser Michael Flynn and Trump campaign foreign policy aide George Papadopoulos have pleaded guilty to lying to investigators about their foreign contacts and are cooperating with investigators.
On Friday, Mueller's team said that it had turned over more than 590,000 records to Gates, among them emails, financial and corporate records — including 2,200 designated by prosecutors as "hot" or high-priority — and copies of information on 87 electronic devices such as laptops and phones collected through 19 search warrants. Thirty-five of the devices were seized from Manafort's house, the filing says.
The number of records in the case has ballooned since prosecutors made a similar disclosure Dec. 8, when they gave both defendants some 400,000 items, including contents of 36 memory devices, and disclosed 15 warrants.
The latest four-page filing states that the government's investigation has continued and that on Friday, the government turned over a sixth batch of records, including foreign bank records obtained since the two men were charged.
In a footnote, prosecutors noted that they are not turning over to Gates records that they obtained from Manafort that are not relevant to Gates's case, and vice versa. They also wrote that "electronic evidence seized from Manafort's residence was previously made available to Manafort earlier this year (to the extent that the FBI was able to access the devices/media seized at that time)."
The special counsel's office recently added a veteran cyber-prosecutor to its team.
The Washington Post reported Wednesday that Ryan K. Dickey was assigned to Mueller's team in early November from the Justice Department's computer crime and intellectual-property section, joining 16 other lawyers.