Homeland Security Committee Chairman Ron Johnson said DOJ Inspector General Michael Horowitz investigated the case and whether there was any wrongdoing.
The Justice Department told CNN that it was reviewing Grassley’s letter. A representative of Muller declined to comment.
CNN has reached out to Weissman for comment.
Other users whose phones were marked as “erased” include James Quarles, Rush Atkinson, and Greg Andress. (Many of those whose names have been erased have been renamed.)
President Donald Trump and his supporters have long sought to reject the FBI’s Russia investigation and Muller’s findings, questioning whether the FBI also had reason to open an investigation into its presidential campaign.
Trump spoke about Weissman during his Saturday evening rally in Nevada, saying there “have to be replicas for the deletion”.
In July 2016, the FBI launched an investigation into Russian interference in the 2016 election and possible relations between Kremlin and Trump campaign officials. Muller commanded the investigation in 2017 when he was appointed as special counsel.
On Barr’s instruction, the Justice Department launched an investigation at the core of the FBI Russia investigation last year.
Barr dismissed Horowitz’s contention that the FBI had properly opened a full investigation, called Crossfire Hurricane, based on the evidence he had.
Trump and Republicans point to text messages between former FBI staffers Peter Strzok and Lisa Page to argue that an anti-Trump bias exists in the bureau.
Horowitz stated in his report that Strozok and Page did not influence the start of the investigation or exclude political bias.
This story has been updated with additional development.
Ivan Perez of CNN contributed to this report.