In a section of the letter titled “Missing documents,” Grassley and Feinstein said Kushner had handed over some materials but omitted communications that mentioned some of the people connected to the investigation into Russian meddling in the 2016 election.

“If, as you suggest, Mr. Kushner was unaware of, for example, any attempts at Russian interference in the 2016 presidential election, then presumably there would be few communications concerning many of the persons identified,” the lawmakers wrote.

Grassley and Feinstein also alluded to documents they received from other witnesses on which Kushner was copied.

“Other parties have produced September 2016 email communications to Mr. Kushner concerning WikiLeaks, which Mr. Kushner then forwarded to another campaign official,” they wrote. “Such documents should have been produced...but were not.

“Likewise,” the letter continued, “other parties have produced documents concerning a ‘Russian backdoor overture and dinner invite’ which Mr. Kushner also forwarded. And still others have produced communications with Sergei Millian, copied to Mr. Kushner. Again, these do not appear in Mr. Kushner’s production despite being responsive to the second request. You also have not produced any phone records that we presume exist and would relate to Mr. Kushner’s communications regarding several requests.”

They asked Kushner to turn over all responsive documents by Nov. 27.

According to the lawmakers, Kushner’s attorney suggested providing some documents might “implicate the president’s Executive Privilege.”

Special counsel Robert Mueller’s investigators reportedly issued a subpoena to President Donald Trump’s campaign last month, requesting Russia-related documents from over a dozen top officials, reports the Wall Street Journal.

The subpoena, issued in mid-October, reportedly requested documents and emails with keywords related to Russia but didn’t compel any officials to testify before Mueller’s grand jury, an unnamed source told the Journal.

This is the first report of Mueller compelling the Trump campaign to hand over information.