"According to preliminary information, three people were killed," Russia's investigative committee said in a statement.

It said they were likely to be "passengers of a car that was near the truck that exploded."

The statement said the bodies of two victims -- "a man and a woman" -- had been lifted out of the water.

It said their identities were being confirmed, giving no details on the third body.

The blast took place early on Saturday morning, with authorities saying two lanes had partially collapsed.

Investigators said a resident of Russia's southern Krasnodar region, which it did not name, was the owner of the car.

"Investigative actions have been launched at his place of residence," the investigators said.

They added that the truck's "route movement documentation" was being studied.