During the construction of Kerameikos metro station for the expanded Athens Metro, a plague pit and approximately 1,000 tombs from the 4th and 5th centuries BC were discovered. The Greek archaeologist Efi Baziotopoulou-Valavani, who excavated the site, has dated the grave to between 430 and 426 BC. Thucydides described the panic caused by the plague which struck the besieged city in 430 BC. The epidemic lasted for two years and killed an estimated one third of the population. He wrote that bodies were abandoned in temples and streets, to be subsequently collected and hastily buried. The disease reappeared in the winter of 427 BC.