IBTimes | Theodore Postol, a professor emeritus at the Massachusetts Institute of Technology (MIT), issued a series of three reports in response to the White House's finding that Syrian President Bashar Al-Assad perpetrated the attack on 4 April.
He concluded that the US government's report does not provide any "concrete" evidence that Assad was responsible, adding it was more likely that the attack was perpetrated by players on the ground.
Postol said: "I have reviewed the [White House's] document carefully, and I believe it can be shown, without doubt, that the document does not provide any evidence whatsoever that the US government has concrete knowledge that the government of Syria was the source of the chemical attack in Khan Sheikhoun, Syria at roughly 6am to 7am on 4 April, 2017.
"In fact, a main piece of evidence that is cited in the document point to an attack that was executed by individuals on the ground, not from an aircraft, on the morning of 4 April.
"This conclusion is based on an assumption made by the White House when it cited the source of the sarin release and the photographs of that source. My own assessment is that the source was very likely tampered with or staged, so no serious conclusion could be made from the photographs cited by the White House."
The image Postol refers to is that of a crater containing a shell inside, which is said to have contained the sarin gas.
His analysis of the shell suggests that it could not have been dropped from an airplane as the damage of the casing is inconsistent from an aerial explosion. Instead, Postol said it was more likely that an explosive charge was laid upon the shell containing sarin, before being detonated.