(CNN) - Former Roger Stone employee Andrew Miller has turned over records related to his old boss to a federal grand jury, including the now-indicted political operative's schedule from the 2016 Republican National Convention, his attorney said Friday.
Miller testified about his former employer to the grand jury last week, and during that testimony -- which he had held off for a year -- prosecutors asked for more records that he had about Stone.
The grand jury subpoenaed Miller for all text messages between Stone and him from early October 2016 to mid-March 2017, and the written agenda for Stone while he was at the Republican National Convention in 2016, according to Miller's lawyer, Paul Kamenar.
The recent grand jury activity indicates prosecutors are still looking into Stone for potentially new charges, though it's not clear if Stone or someone else is the target in the investigation.
Miller previously handed over documents about Stone in special counsel Robert Mueller's investigation, and was originally subpoenaed to testify as part of that probe.
Stone's was the last criminal case opened by Mueller before he ended his investigation in March.
Stone has pleaded not guilty to obstruction, lying to Congress and witness intimidation related to his efforts to reach WikiLeaks in 2016 to help the Trump campaign.
A different grand jury from the one Mueller originally used heard Miller's testimony last week. Miller discussed Stone, the 2016 Republican National Convention, his relationship with Stone since then, and what he knew of Stone's contact with Julian Assange and WikiLeaks, Kamenar said at the time.
"It's hard to say where they're going on this," Kamenar said, adding that "there could very well be a continuing investigation" into Russian interference in the 2016 election but that Miller did not have much information to help prosecutors.
Miller said last week that he had worked for Stone -- calling him "Uncle Roger" -- for 13 years, as a driver and helping to manage Stone's emails and website. Miller has not worked with Stone since the election, Kamenar said.
Miller does not need to testify again to the grand jury, Kamenar said he was told.
CNN's Caroline Kelly contributed to this report.
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