A video posted by the group appears to show militants with the weapons bundle, including grenades and mortars near the battleground town of Kobani.
The video opens with a shot of a black parachute draped across a desert landscape.
An IS fighter wearing a black balaclava and military fatigues is then seen going through the crates, revealing rocket propelled grenades and other explosives.
"These are some of the American supplies that were air-dropped to the infidel Kurdistan Workers Party," he's heard saying.
"This is some of the ammunition air-dropped by the Americans to the Kurdish People's Protection Unit.
"Praise to God, now they are spoils for the Mujahideen."
The United States Defense Department is still examining the video.
US military authorities have acknowledged that at least one drop did go astray, but it was later destroyed in an airstrike to prevent it from falling into the wrong hands.
When asked if the bundle seen in the video was the one destroyed, Pentagon spokesman Rear Admiral John Kirby would neither confirm nor deny.
"We're aware that one bundle did not make it into the right hands and you saw the (Central Command) release that they destroyed it from the air," he said.
"All of that doesn't take away from the notion that there's videos out there and that it could in fact be that bundle. We just don't know.
"I can tell you that analysts are working as fast as they can to try to validate it, and when we have something that we can give you we'll provide it."
The bundle is one of the 28 dropped into Syria to supplement airstrikes against IS fighters near Kobani.
The main Syrian Kurdish army has welcomed the airdrops and is asking for more as the battle rages well into its second month.
Nozhin Youssif from the Kurdish Democratic Union Party said Kurdish fighters have greater need of weapons than food and water.
"The dropping of other supplies, including medicine is also necessary because the Islamic State's shelling has destroyed hospitals, clinics and pharmacies in Kobani," she said.
"These supplies have definitely helped boost morale in Kobani. And the arrival of these weapons will make us more determined to defeat the militants."
United Nations envoy Staffan de Mistura, who's been appointed to mediate a political solution in Syria to end the war, has warned thousands of people could be massacred if Kobani falls to Islamic State.
But UN Secretary-General Ban Ki-Moon says responding only with military force in Syria will simply bring further violence from new groups.
"Our long-term strategic objective in Syria remains a political solution," he said.
"A purely military response to this vicious new threat could ultimately contribute to the radicalisation of other Sunni armed groups and spark a cycle of renewed violence.
"I urge your full support for my special envoy's efforts to reduce the suffering of the Syrian people and contribute to a political solution."
In Iraq, a mainly Shiite area in the capital Baghdad has been rocked by three car bombs that have killed at least 18 people.
Two blasts hit the car park of a large restaurant while a third exploded near a police patrol that passed by later.
More than 50 other people were wounded.
There was no immediate claim of responsibility for the bombings but I-S has admitted to carrying out similar attacks in recent days.
Share
