House Oversight Committee Chairman Elijah Cummings (D-Md.) has demanded private communication records of first daughter Ivanka Trump and other White House officials, including Jared Kushner’s encrypted WhatsApp messages, which he says were exchanged with “foreign leaders.”

Cummings called for the records in a letter Thursday to Pat Cipollone, the counsel to the president. He accused the White House of “obstructing” the committee’s investigation and of violating federal law by refusing to provide the records that were part of official business.

Cummings’ reference to Kushner’s WhatsApp messages comes in the wake of revelations last month that President Donald Trump intervened on behalf of his son-in-law and senior White House adviser to demand top-secret security clearance for Kushner against the recommendations of the FBI. The Kushner family’s company does business with foreign countries.

Cummings noted that Kushner’s attorney Abbe Lowell told him and then-chairman Trey Gowdy (R-S.C.) late last year that his client had been “using the messaging application What’sApp as part of his official White House communication with foreign leaders.” Lowell “could not answer whether Mr. Kushner’s communications included classified information — which would be a major security breach,” Cummings added. The congressman said when Lowell was asked about classified information, he responded, “That’s above my pay grade.”

Asked how Kushner, Ivanka Trump’s husband, preserved his communications, as required by law, Lowell said he took “screen shots” of them and forwarded them to his official email account or to the National Security Council.

Lowell denied in a responding letter to Cummings on Thursday that he said Kushner communicated via WhatsApp with foreign “leaders,” adding: “I did not specify who they were.” He said Kushner has “numerous friends and contacts abroad” and insisted that he follows “protocols.” CNN reported last year that Kushner used WhatsApp to communicate with Saudi Crown PrinceMohammed bin Salman.

Cummings’ letter was sent as part of the committee’s investigation into the use of “personal email and messaging accounts” at the White House in violation of the Presidential Records Act and of White House policy, the congressman noted. He complained that the White House has failed to produce documents demanded by the committee throughout much of 2017 and 2018. The committee launched the investigation when the Republicans held the House majority.

“As you know, the White House has not produced a single piece of paper to the Committee in the 116th Congress — in this or any other investigation,” Cummings complained in the letter.

Trump made Democratic rival Hillary Clinton’s use of a personal email server while secretary of state a cornerstone of his attacks on her during his presidential campaign. His repeated attacks triggered chants of “Lock her up” by his supporters. Trump has continued to call for a new investigation of Clinton’s emails, even though her communications were scrutinized and cleared in two FBI probes.

Ivanka Trump was found in 2017 to have used a personal account to send hundreds of emails to Cabinet officials, White House aides and assistants in violation of federal rules, The Washington Post reported. She has insisted there is no comparison to what Clinton did because her emails were “preserved” and did not include “anything of substance.” Yet the emails have yet to be provided to the House Oversight Committee.

Cummings said Lowell told him the first daughter continues to use her personal email account for official communication. Lowell insisted in his letter to Cummings that she forwards all communication to her official White House account.

Cummings gave Cipollone until April 4 to comply with his committee’s demands for records. Otherwise, he warned, the panel would be forced to consider “alternative means,” which could include subpoenas.

White House spokesman Steven Groves said in a statement that the White House “has received Chairman Cummings’ letter of March 21st. As with all properly authorized oversight requests, the White House will review the letter and will provide a reasonable response in due course.”