**CONTAINS GRAPHIC IMAGES**
After taking fire from snipers in Damascus, the U.N. team of chemical weapons experts reaches a medical clinic where victims of an alleged gassing are believed to be recovering.
Amateur video, which Reuters cannot independently verify, appears to show the U.N. members examining the victims alongside doctors.
The U.N. had arrived to investigate other reported chemical weapons attacks, but when video surfaced last week showing this apparent attack, the team demanded access.
Men, women and children could be seen gasping for air.
That video also could not be independently verified.
Estimates of the attack's death toll range from 500 to more than 1,000.
U.N. Secretary General Ban Ki-Moon has condemned both the chemical weapons attack and the firing on his investigators.
Meanwhile, the U.S. is already weighing options for a response, including possible military action.
Defense Secretary Chuck Hagel:
(SOUNDBITE) (English) UNITED STATES DEFENSE SECRETARY CHUCK HAGEL SAYING:
"We will get the facts. And if there is any action taken it will be in concert with the international community and within the framework of any legal justifications."
Syrian ally Russia says rebels may have been behind the attack.
Russian Foreign Minister Sergei Lavrov:
SOUNDBITE) (Russian) RUSSIAN FOREIGN MINISTER SERGEI LAVROV, SAYING:
"If anybody thinks that bombing and destroying the Syrian military infrastructure, and leaving the battlefield for the opponents of the regime to win, would end everything - that is an illusion."
Syrian President Bashar al-Assad has denied all responsibility for the attack.