At least 15 people have died, two are missing and 17 have been seriously injured in floods in Greece, as damage climbed to billions of euros.
Water rushing down ravines from the mountains toward the coastal lowlands after an overnight deluge was blocked from flowing to the sea by debris, resulting in the flooding of coastal towns.
In other areas, decades of illegal construction, some of it directly on outflow channels, blocked water and caused overspilling.
Prosecutors have launched an investigation in the affected regions of Elefsina and Megara.
Entire towns were ravaged and sections of the main Korinthian highway on the west coast were swept away, the state radio reported. Early official estimates placed the cost at billions of euros.
Prime Minister Alexis Tsipras declared a period of national mourning. "These are very difficult moments for Greece. We are living a great disaster," he said in a state address.
The storm, which local meteorologists nicknamed "medicane" - a Mediterranean hurricane - is set to linger for days, drop more rain and cause further flooding.
It is the product of a massive low-pressure area above the sea and unseasonably warm weather.