Two cranes being used in the restoration of a bridge in a central Dutch city have fallen onto a row of buildings and local media report up to 20 people have been injured.

Ton Koot, a spokesman for the local fire brigade in Alphen aan den Rijn, told national broadcaster NOS that heavy machinery was being moved to the scene Monday in case people are trapped under rubble and need to be rescued. Koot said he didn't know how seriously injured the victims were.

Amateur video shown on NOS showed the cranes on a pontoon carrying a large section of the bridge when they began to shift and topple over onto a row of houses.

Further details weren't immediately available.