Flash floods caused by heavy rain in Greece killed at least 15 people in three rural towns west of the capital Athens on Wednesday.
The towns of Mandra, Nea Peramos and Megara are home to many factories and warehouses on the rural outskirts of the city.
Officials have compared the flooding overnight to a waterfall, coming down the mountains of the western Attica region.
“The situation is very difficult; the Niagara Falls came down and could not be stopped,” the deputy regional governor, Yiannis Vassileiou, told state-run TV network ERT.
The floods have been described by area mayors as the worst in 20 years.
“Everything is lost. The disaster is biblical,” Mandra Mayor Ioanna Kriekouki told ERT.
Greek Prime Minister Alexis Tsipras has declared a national day of mourning for the flood victims and expressed his support for their families.
“It is a very difficult time for all of Greece," Tsipras said in a statement. “We are experiencing a great disaster.”
Three people are being treated at local hospitals and one person remains missing, according to the local fire department.
“We have people who are trapped ... we need machinery to get them out of their homes,” said Kriekouki, who was also stuck in her home.
Roads in the coastal town of Nea Peramos were destroyed, Deputy Mayor Stavros Fotiou told ERT. Fotiou said that nearly a third of the town's homes are flooded.
“The walls collapsed, the cars were carried away and they broke everything here. There is nothing left,” Madras resident Marina Kolia said. “Water is everywhere in the house.”
Many of the victims were found dead in or near their homes. Some of the bodies were found floating in the sea.
The death toll from the flooding is expected to rise once rescue teams access all the affected areas. The prime minister’s office said that 87 people have been rescued. The fire department has received more than 600 calls for help from the locals and dispatched nearly 200 firefighters.
“Access to the area is difficult; debris has nearly reached the height of homes,” said fire department spokesman Yiannis Kapakis.
More heavy rainfall was expected.
Several areas were experiencing electricity and water outages due to debris. Town officials said repairs could take up to five days.