House Oversight and Government Reform Committee Chairman Darrell Issa (R-Calif.) is plowing forward with his Benghazi investigation by issuing four deposition subpoenas to State Department officials.

In a letter to Secretary of State John Kerry, Issa noted numerous attempts to interview the officials, including requests on April 29 and May 17. Investigators with the committee were only able to interview one of the 13 individuals sought for questioning and the interview was facilitated without the help of the State Department.

The four subpoenaed officials are Eric Boswell, Former Assistant Secretary, Bureau of Diplomatic Security; Scott Bultrowicz, Former Principal Deputy Assistant Secretary and Director of the Diplomatic Security Service, Bureau of Diplomatic Security; Elizabeth Dibble, Former Principal Deputy Assistant Secretary, Bureau of Near Eastern Affairs; and Elizabeth Jones, Acting Assistant Secretary, Bureau Near Eastern Affairs.

All of the bureaus were cited by the State Department’s Accountability Review Board as having deficiencies that led to inadequate security at the time of the Benghazi attack.

“These persistent delays create the appearance that the Department is dragging its feet to slow down the Committee’s investigation,” Issa wrote Kerry. “It does not require weeks of preparation to answer questions truthfully. These delays also take us further in time away from the dates of the events in question.”

“The Committee has a bipartisan interest in holding a public hearing to examine the Accountability Review Board as soon as possible. Based on the interview schedule that my staff laid out in April, it was my expectation that we would have interviewed a half dozen witnesses at this point.”

Issa told Kerry the committee is left “with no alternative but to issue subpoenas to compel testimony from these important witnesses.”

“It is irresponsible for the Department to unnecessarily expose its employees to the risks inherent in being named in a congressional subpoena. By its very nature, a subpoena can carry the implication that the witness is being uncooperative,” he continued. “In this case, that is an unfortunate and misleading consequence since it is the Department, and not the individuals themselves, that appears to be dictating the timetable.”