Now that Assad is in control of Douma, his forces are keeping chemical investigators away saying it is too dangerous for them, while shepherding journalists on guided tours to tell them there was no chemical attack.

Some of the people say there was a chemical attack but it was a false-flag attack carried out by Islamist rebels.

It is hard to determine what parts of this are true, but if one of those stories were true, I don't think anyone would be asserting the other one. Therefore, I think that Assad carried out the chemical attack. But I can't say that is proven.