(CNN) -- Inspectors overseeing efforts to destroy Syria's chemical weapons have examined one more site in the war-torn country, leaving only one to go.
The joint mission between the Organisation for the Prohibition of Chemical Weapons and the United Nations has verified 22 of the 23 sites disclosed by Damascus, the mission announced Thursday.
The latest site, in Aleppo, was one of two that could not be visited earlier for safety reasons, the mission said in a statement.
"As per the declaration by Syria, the site was confirmed as dismantled and long abandoned with the building showing extensive battle damage," the statement said.
But while the inspection progresses, the United States is looking at new classified intelligence suggesting that Syria might not fully declare its chemical weapons stockpile, CNN has learned.
The intelligence is not definitive, but "there are various threads of information that would shake our confidence," one U.S. official said. "They have done things recently that suggest Syria is not ready to get rid of all their chemical weapons."
CNN has spoken to several U.S. officials with access to the latest intelligence on Syria, who confirmed the information. All declined to be identified because of the sensitivity of the data. U.S. intelligence agencies, the Defense Department, the State Department and White House are all reviewing the information.
CNN's Josh Levs and Barbara Starr contributed to this report.