A State Department document shows the U.S. Embassy in Libya had deep concerns about security prior to the fatal attack on Sept. 11.

A memo obtained by ABC News shows the embassy requested an extension of a 16-member security team's deployment earlier this year.

The memo read, "Quite simply, we cannot maintain our existing levels of embassy operations...without a continued SST (Security Support Team) presence."

The State Department said that request was granted in February.

Now, some are questioning why that team was allowed to leave when the four-month extension ended.
    
Lt. Col. Andrew Wood, the team's leader, said he and Ambassador Chris Stevens agreed that his team should not be pulled out in August.

A State Department official, however, said it did not receive a request for another extension. The official also said the team was replaced by an equal number of people with similar skills.   

Stephens and three others died in a terrorist attack on the American Consulate in Benghazi on Sept. 11.
    
Lt. Col. Wood will testify at a congressional hearing looking into the attacks on Wednesday.