Residents confirmed that there appeared to be a massive military operation under way early Wednesday, with warplanes dropping bombs and artillery firing for hours.
Staff at the Mezzeh University hospital told CNN they received many casualties Wednesday from the area allegedly hit by the attack. But, they said, the casualties showed no signs of having been subjected to chemical agents.
However, experts who have viewed footage purportedly from the scene say it indicates that some form of chemical seemed to have been used.
The U.N.-Arab League envoy to Syria, Lakhdar Brahimi, says he believes the recent violence in Ghouta emphasizes the need for a political settlement between the Syrian government and opposition, his spokeswoman Khawla Mattar told CNN on Friday.
"The human loss is unacceptable and we have to do something about getting all parties, particularly the two Syrian sides ... to the Geneva II (peace talks) sooner than later," Mattar said.
A previous meeting of world leaders aimed at taking steps to bring peace to Syria took place in Geneva, Switzerland, just over a year ago. No date has been set for a second Geneva conference, originally expected in June, but Ban said he was working with Kerry and Lavrov to convene it "as soon as possible."
There is no indication when the U.N. inspection team, currently in Damascus, will be able to travel to the site of the alleged attack, Mattar added.
The allegations of chemical weapons use spurred calls Thursday for the United Nations to act.
Turkey's foreign minister, Ahmet Davutoglu, said that "all red lines" have been crossed in Syria and that the United Nations cannot be indecisive about chemical weapons attacks there.
His French counterpart, Laurent Fabius, said force must be used if the claims of chemical weapons use were proved, although he ruled out the use of ground troops.
Their comments came after the U.N. Security Council held a short-notice briefing late Wednesday to discuss the situation. Russia and China -- consistent allies of the Syrian government -- reportedly blocked a formal resolution.
Obama has directed the U.S. intelligence community to urgently gather additional information to try to assess whether chemical weapons were used Wednesday, State Department spokeswoman Jen Psaki said Thursday.
At this time, she said, the United States is unable to "conclusively determine" chemical weapons use, but is focused on trying to nail down the facts, along with its international partners.
Psaki said, as she has before, that if reports of chemical weapons use prove true, the president has a range of responses available.
Later, a senior defense official told CNN that "the military continues to refine options for Syria to be prepared for whatever the president might request down the line."
U.N. High Commissioner for Human Rights Navi Pillay said the matter is "of utmost urgency" and the "allegations are exceptionally grave."
Pillay urged the government and opposition to allow investigators "to examine the site of the alleged attacks without any delay or obfuscation."
Meanwhile, a U.S. defense official said Friday the United States has added one more destroyer to the eastern Mediterranean fleet.