Police say four firefighters have been injured, three of them seriously, in explosions as they tackled a blaze at warehouses in western Germany.

The fire in Hilden, near Cologne, broke out in the early hours of Sunday. Police said in a statement that the blaze expanded with "several detonations" after the firemen arrived at the scene.

They say that packaging, including paper and plastic, along with car tires, was stored at the site. Forty people were evacuated from nearby houses.

The fire was under control after about five hours. The cause was unclear.