DAMASCUS -- International inspectors say Syria and Russia blocked them Monday from reaching Douma, the Syrian town where dozens were killed in a suspected poison gas attack nine days ago. The U.S. and its allies say Syrian President Bashar al-Assad carried out the deadly chemical weapons attack.

Douma was the last rebel-held town near Damascus, and the attack led to the weekend missile strikes by the U.S., Britain and France, targeting Syria's alleged chemical weapons facilities. On Monday, CBS News made it to the house where the suspected chemical attack took place.

"All of a sudden some gas spread around us," one neighbor recounted. "We couldn't breathe, it smelled like chlorine."

Syrian forces recaptured the area from rebels over the weekend. That means they now control the building where the video was taken. Nasr Hanan's brother Hamzeh is seen in that activist video lifeless and foaming at the mouth. In the kitchen, he told us how his brother had tried to wash-off the chemicals.

We asked him to take us to where the missile allegedly hit, and he showed us where a missile was neatly resting.

A missile in Douma, Syria CBS News

Syria insists there was no chemical attack, while the U.S., France and U.K. blame Syria. Since those coalition airstrikes, Syrian President Bashar al-Assad's government has tried to show it was unaffected. On Monday, they highlighted their military gains, as Syrian forces drove through Douma.

Rebels had run the Damascus suburb since 2012, and the intense campaign to recapture it started in February, with Russia's help.

CBS News also went to an apparent bomb-making factory for rebels in the heart of Douma, where there were the makings of fins for mortars, and a bin of what appears to be homemade grenades. Down a network of tunnels, there were more weapons stored.

The human toll of the fighting was evident in the main square. Hundreds of thousands of civilians have been living there, many without food for months, and you could see the desperation, with people just hoping for some bread.

We asked one mother of five why she didn't leave, if the fighting had been so bad.

"We tried more than once," she told us. "But the rebels wouldn't let us go."