The chairman of the House Oversight Committee has sent a letter to the company that handled the technical side of Hillary Clinton's private email server. Rep. Jason Chaffetz wants to know why an employee of Platte River Networks (PRN), which was under contract with Clinton to handle the server, deleted large amounts of email after the Clinton team received a congressional subpoena for the material, and why a PRN technical employee, apparently the one who performed the actual deletions, asserted a legal privilege and refused to tell the FBI what was said on a conference call he took part in with Clinton's attorneys on March 25, 2015, around the time the deletions were performed.

The FBI has released a heavily-redacted version of its summary report on the Clinton email affair, plus a writeup of Clinton's own interview with agents. That's all the Bureau has made public, although it has provided writeups of other interviews and other material to Congress under tight viewing restrictions.

In a letter to PRN, Chaffetz referred several times to the unreleased summaries of two FBI interviews with the technician involved:

The summaries of the FBI's interviews with a PRN engineer show that within days of a conference call with Secretary Clinton's lawyers, the engineer deleted archives of Secretary Clinton's emails, despite knowing those records were covered by preservation orders and a subpoena from Congress. The same interview summaries show that days after the conference call, a work ticket was created at PRN relating to the administration of Secretary Clinton's email server. The contents of the ticket were not provided. Forensic analysis of Secretary Clinton's private email servers by the FBI revealed that Secretary Clinton had not turned over all work-related emails, despite her claims to the contrary, meaning some responsive records may have been included in the archives PRN deleted. Due to the PRN engineer's use of a program called BleachBit, however, the FBI was apparently unable to retrieve those archives. BleachBit is designed to "shred the files to prevent recovery."

The FBI summary report suggests the PRN technician initially misled agents about the events leading up to the deletions sometime between March 25, when the conference call took place, and March 31, 2015. Then, when the PRN engineer was asked about the conference call between himself, Clinton attorney David Kendall and top Clinton aide Cheryl Mills, the engineer refused to answer the FBI's questions.

According to the FBI report, "PRN's attorney advised [the redacted name of the PRN technician] not to comment on the conversation with Kendall based upon the assertion of attorney-client privilege."

The new Chaffetz letter to PRN says it a little differently: "When asked about the conference call between Secretary Clinton's attorneys and the PRN engineer, the engineer refused to answer the FBI's questions and asserted a legal privilege. The FBI's investigative file is not clear as to whether the engineer asserted the attorney-client privilege, the Fifth Amendment privilege, or both."

In the letter to PRN, Chaffetz said the timeline of events "raises questions as to whether the PRN engineer violated federal statues that prohibit destruction of evidence and obstruction of a congressional investigation when the engineer erased Secretary Clinton's email contrary to congressional preservation orders and a subpoena."

In addition, Chaffetz said the "sequence of events leading up to the destruction of Secretary Clinton's emails … raises questions about whether Secretary Clinton, acting through her attorneys, instructed PRN to destroy records relevant to the then-ongoing congressional investigations."

In the letter, Chaffetz asked PRN a series of questions about the technician's assertion of privilege. Just what was it? Who was who's attorney? Did the technician or others at PRN sign non-disclosure agreements about their work for Clinton? Chaffetz gave the company until Sept. 13 to answer.

Another document that might shed light on the deletions is a March 27, 2015 letter from Kendall to House Benghazi Committee chairman Trey Gowdy. The letter was dated just two days after the conference call that the PRN technician refused to discuss. In it, Kendall addressed Gowdy's request to have a neutral third party examine Clinton's server. The short version of Kendall's answer: Forget it, Trey. There's nothing there.

"To avoid prolonging a discussion that would be academic, I have confirmed with [Secretary Clinton's] IT support that no e-mails from for the time period January 21, 2009 through February 1, 2013 reside on the server or on any back-up systems associated with the server," Kendall wrote Gowdy. "Thus, there are no e-mails from Secretary Clinton's tenure as Secretary of State on the server for any review, even if such review were appropriate or legally authorized."

Whether Kendall's statement that he had "confirmed" with Clinton's IT team was a reference to the conference call just two days earlier is not clear. But there's no doubt that Kendall, on March 27, seemed pretty sure there were no emails left on Clinton's server.

The FBI summary report said the PRN technician told agents he performed the deletions "sometimes between March 25-31, 2015."

The events of March 2015 are shaping up as critical in the investigation of the email affair. At the beginning of the month, March 2, the New York Times reported the existence of the secret Clinton email system. The next day, the House Benghazi Committee sent a letter ordering Clinton to preserve all emails that might be relevant to its investigation. The day after that, March 4, the committee sent a subpoena. By the end of the month, March 31, the deletion and server-wiping had taken place.

Exactly how it all happened, however, is still not clear.