Mohammed el-Shaiky/AP Photo

The State Department today condemned an explosion that damaged Libya's Foreign Ministry in Benghazi, one year after the now-infamous attack on the U.S. diplomatic facility there.

"We condemn this violent act, as it threatens to undermine Libya's democratic transition as well as the legacy of Libya's revolution in which the Libyan people made their voices heard through peaceful means," State Department spokeswoman Jen Psaki said at today's department press briefing.

A car bomb exploded this morning in the eastern Libyan city. U.S. Ambassador Chris Stevens died a year ago today in an attack that brought criticism to the State Department and fueled a year of investigation and accusations by Republicans in Congress who blamed the administration for the attack.

The State Department began the day on a somber note, as Secretary of State John Kerry recalled the attack, and its effect on State Department employees, in a written statement.

"I lost friends - people I'd known a long time - who were on those flights that left from Boston on the first 9/11. I knew Chris Stevens from the Senate Foreign Relations Committee and heard his passion for what America stood for in Libya," Kerry said. "I mourned him, Sean Smith, Glen Doherty and Tyrone Woods last year at Joint Base Andrews along with many of you. From the other end of the Washington Mall, I and my colleagues in Congress shared your loss even as we admired your service."

The anniversary also brought renewed criticism from congressional Republicans, who have hounded former secretary of State Hillary Clinton and Kerry, her successor, in seeking answers for why the Benghazi facility wasn't more heavily guarded.

Both secretaries have bristled at times at Republicans' questions. Most recently, Kerry confronted questions about Benghazi during congressional hearings on Syria.

Seeking to interview survivors of the 2012 Benghazi attack, House Oversight Committee Chairman Darrell Issa, R-Calif., penned a letter to Kerry Tuesday threatening to subpoena the State Department if it does not make them available.

House Speaker John Boehner, in a written statement this morning, accused the administration of failing to comply with subpoenas and make individuals available to Congress.

"In short, this administration hasn't been upfront with the American people or this Congress. Republicans will not stop until we get to the truth," Boehner wrote.

State spokeswoman Psaki said those survivors could be in danger if their identities are revealed. She also hinted that none of them wants to testify.

"Interviews of these individuals outside of the criminal justice process would pose risks that could jeopardize the law enforcement efforts, and … should their identities become public, they may become targets, putting their lives as well as those of their families and the people they protect at risk," Psaki said.

Responding to the criticism from Boehner and Issa that the department has prevented those survivors from testifying, Psaki replied, "That implies an interest from any of the individuals he's requested in participating."