Initial U.S. intelligence did not show that chemical weapons were used in an attack in Syria's Aleppo province Tuesday, U.S. officials said Thursday.

Analysis of a video of Syrian victims hospitalized after the strike, which killed at least 15 others, suggested they were not suffering from a chemical weapons attack or being treated as though they were in such an attack, a U.S. military official was quoted by the CNN as saying.

"The actions in the video don't match up to a chemical weapons response," said the official, who added that this was only a preliminary conclusion and the investigation would continue.

A second U.S. official also told CNN that "there are strong indications now that chemical weapons were not used by the regime (of President Bashar al-Assad) in recent days."

U.S. analysts believed it was possible the victims in the video were deliberately exposed to, or in some fashion hit with "caustic " agent such as chlorine. That was different from using a chemical weapons, such as a nerve or blister agent, as defined by international treaties, the report said.

U.S. President Barack Obama has warned before that the use of chemical weapons by the Syrian government would be a "game-changer " for the U.S. to change its policies toward Syria. Washington has so far refused to intervene militarily in the Syrian conflict, though it has provided non-lethal assistance to the rebels fighting the Assad government.

Earlier, the Syrian government accused the rebels of firing a rocket stuffed with chemical materials in the Tuesday strike in northern Aleppo province. But White House spokesman Jay Carney on Tuesday said that "no evidence" showed that the rebels had used chemical weapons in their battle against the government troops.