Update from the BBC:
Security camera footage released on social media showed a truck - allegedly from the Russian city of Krasnodar, an hour's drive from the crossing - moving west across the bridge at the time of the explosion.
Russian officials named a 25-year old Krasnodar man, Samir Yusubov, as the owner of the truck, and said an older relative, Makhir Yusubov, was the driver.
In a statement last night, the head of President Zelensky's office, Mykhailo Podolyak, seemed to endorse Moscow's truck bomb theory.
"The answers should be sought in Russia," he said in a statement.
The explosion, he said, was the result of infighting between different parts of Russia's security establishment.
"This is a concrete manifestation of the conflict between the FSB [Russia's internal intelligence service] / PMC [private military contractors, like the Wagner Group] on the one hand, and the Ministry of Defence / general staff of the Russian Federation on the other hand," he said.
The names (Samir and Makhir Yusubov) indicate they're Muslim. More footage was available today, and while it's hard to tell, the part of the collapsed roadway visible above the water surface, seems intact, with no crater blast area, indicating that the explosion may have come from below, but that section could be under water.
