A truck has fallen off the Ojuelegba Bridge in Lagos, smashing into several vehicles below, multiple posts on Twitter said.
Some witnesses said it was not the truck, but its plywood content that spilled onto the vehicles on the street below.
The accident on Tuesday compounded the gridlock in the area.
The number of casualties is unknown yet.
Similar accidents had happened in the past, with containers rolling down from the bridge.
On Wednesday, 2 September 2015, a container on a trailer, heavily loaded with cement, also fell and landed on two cars.
Three members of the same family occupying one of the vehicles all died. The family sued both the Federal and Lagoa State governments and the owners of the truck.