American military officials told CNN on Tuesday that radar, signals intelligence, and aerial surveillance all suggest that Russian aircraft were responsible for airstrikes on an aid convoy near Aleppo, Syria that killed at least 20 people.
"All the evidence we have points to that conclusion," one official told CNN.
The Red Crescent aid convoy was heading to a village just outside Aleppo Monday night when 18 of its 31 trucks, which were carrying UN supplies, were struck in at least two waves of strikes. As a result, the UN has halted all aid delivery in the country.
The attack occurred shortly after a ceasefire agreement between the Syrian regime and rebels seeking to oust President Bashar al-Assad, which was intended to allow the passage of humanitarian aid, broke down amid renewed fighting.
The Russian military had already denied that Russia or Syria had anything to do with the attacks. Russia's defense ministry released drone footage that they argue proves other factors were at play.
"We carefully studied the video recordings of the so-called activists from the scene and found no signs that any munitions hit the convoy," said Russian military spokesperson Igor Konashenkov, according to Kremlin-owned news agency TASS. "Everything shown on the video is the direct consequence that the cargo caught fire and this began in a strange way simultaneously with carrying out a massive offensive of militants in Aleppo."
While the official explanation was that the convoy had not been hit with munitions, Konashenkov did imply that an offensive from Jabhat al-Nusra, the al-Qaeda linked militant group, had something to do with the deadly strikes.
Later in the day, TASS issued a new report, again quoting Konashenkov, suggesting that the convoy had been accompanied by a "terrorists' truck with a mortar."
"It is not clear who is covering home [sic]: either the mortar is covering the convoy with the White Helmets volunteers or vise versa," the spokesperson said, seemingly implying that the humanitarian aid workers had been working in conjunction with the al-Nusra fighters.
The Syrian Observatory for Human Rights, which employs a network of activists in the country to monitor attacks on civilians, reports that it was a series of airstrikes that took out the convoy in Aleppo.
If Russia is proven responsible for the attack, it would be a black eye for the Putin regime, which spent the better part of Monday condemning an accidental airstrike carried out by the US on a Syrian military position, also near Aleppo.
It's not the first time Russia and America have argued about who was behind an airstrike in Syria. In August, neither country could agree on who was responsible for taking out the Islamic State's second-in-command.
Despite the seeming disintegration of the cease fire, US Secretary of State John Kerry told reporters that the agreement is "not dead" and is planning on meeting his counterparts, including Russian Foreign Minister Sergey Lavrov, again on Friday.
Follow Justin Ling on Twitter: @Justin_Ling