A small team of U.S. commandos was dispatched to assess security at the American consulate in Benghazi, Libya, and train local forces to better to protect that facility following an attack on a U.N. convoy there in April, an administration official told CNN.

The development is one of the strongest indicators yet highlighting the level of concern about security in the region in the time before last month's attack on the Benghazi consulate that killed Ambassador Christopher Stevens and three other Americans.

American intelligence believes it was a deliberate terrorist assault.

Special forces often conduct security assessments in areas deemed more threatening. Their presence and what they found and recommended would have been known to the ambassador, the official said.

The official, who declined to be identified because of the sensitive nature of the information, said there had been security concerns at the site after that U.N. attack.

The U.S. military team recommended a number of changes that included sandbag reinforcement of guard positions at the site and conducted training for local Libyan security personnel. The team was sent because "there was some concern."

The New York Times and the Washington Post first reported many of the details.

Until July of this year, U.S. special operations forces provided some key support for security at the American embassy in Tripoli and occasionally at the consulate at Benghazi until enough contractor and State Department personnel were trained to take over, according to the official.

The military contingent in Libya had first been sent in after the embassy reopened in September of last year following the revolution. At that time, there were not enough qualified and trained local contractors to take on the job and a State Department security team was not yet fully in place.

The military security personnel came from the U.S. Africa Command, which has responsibility for any American military operations in Libya.

After July 2012, the State Department took full responsibility for security operations while military personnel performed other duties, including working with Libyan forces.

Three U.S. officials told CNN that after the April attack, the Pentagon never received a request from the State Department to send military security forces back to Benghazi to secure the site.

While it's always possible there was some informal discussion, the officials are adamant that any such deployment would have required extensive planning within the U.S. government and approval from the Libyan government for the presence of U.S. military personnel, weapons and equipment to counter the mortar and rocket propelled grenade threat in the Benghazi area.