With questions still bubbling about what precautions were taken by the State Department and what might have been known before last week's attacks on U.S. diplomats in Libya, a group of Senators have asked for an official probe of those matters.

In a letter to Secretary of State Hillary Clinton, the group of Senators said recent events in the Mideast show the need for a "thorough interagency security review of embassies in conflict and transitional countries."

Here is the text of the letter from Senators Barbara Mikulski (D-MD), Dan Coats (R-IN), Roy Blount (R-MO) and Bill Nelson (D-FL):

Dear Secretary Clinton:

We join you in condemning in no uncertain terms the vicious attack against the U.S. Consulate in Benghazi, Libya, and the violent demonstrations at the U.S. Embassies in Cairo, Egypt; Sana'a, Yemen; and elsewhere in the region. We especially mourn the tragic loss of Ambassador Stevens and the three other diplomats, who died in honorable service to this nation while working to build democracy and friendship with the people of Libya.

The violence in Benghazi, Cairo, Sana'a and other diplomatic compounds clearly underscores the need for an updated assessment of security protocols and arrangements at our embassies around the world, which house personnel from the State Department and agencies across the U.S. Government. While we laud reports that many Libyan security staff bravely fought to protect U.S. personnel in Benghazi, the incident raises the broader question of the adequacy of indigenous security forces in providing perimeter security, particularly in conflict and transitional countries.

We appreciate that certain security arrangements for U.S. Missions with host countries are both necessary and desirable, and we recognize the professionalism of the Uniformed Secret Service in providing such security to foreign embassies in Washington, D.C. We also recognize the service of the United States Marine Corps in protecting our embassies abroad and of the many Foreign Service nationals who serve our embassies with distinction. However, we believe that the recent incidents in Benghazi, Cairo, and Sana'a serve as an impetus for a thorough interagency security review of embassies in conflict and transitional countries, to be led by the State Department and coordinated with the Intelligence Community and other relevant agencies. Such a review should consider the adequacy of indigenous forces in providing external security, options for increasing internal security at vulnerable missions, and an assessment of additional personnel and resources that may be required to heighten security.

The ferocity and swiftness with which the Benghazi, Cairo, and Sana'a attacks took place attest to the rapidly changing and often unpredictable security environment in which U.S. embassies now find themselves. The events also serve a reminder of how State Department employees, other members of U.S. Missions, and their families put their lives on the line for our country, day in and day out. We share your unwavering commitment to their security and urge you to redouble immediately efforts to assess and verify the appropriateness and capabilities of local security partners. We stand ready to work with you on this important effort.

On Wednesday, the U.S. House will honor the four Americans who died last week in Libya by taking up a resolution to remember their work.

That resolution also sends a message overseas, calling "upon the Governments of Libya, Egypt, and Yemen, in full cooperation with the United States Government, to investigate and bring to justice the perpetrators of these attack."

That came as the White House again rejected reports that the U.S. had intelligence before the attacks, indicating that there was some kind of warning delivered to American officials.

"This is a matter that is under investigation," said White House Press Secretary Jay Carney, "in terms of what precipitated the attack, the motivation for the attack."