Greece's biggest refugee camp faces closure next month unless authorities clean up an "uncontrollable amount of waste" at the site, according to local officials.
A notice, issued by regional governor Chrisinana Kalogirou to the government's minister for migration and the camp director, sets out a 30-day deadline for improvements.
It states that inspectors found broken sewage pipes, overflowing garbage bins, and stagnant water and flies in the toilets,.
A high risk of disease transmission due to overcrowding was also identified at the camp which holds more than 8,300 people living in shipping containers and flimsy tents, more than double its official capacity of 3,100.
Moria, a former military compound consisting of shipping containers and flimsy tents, has long been criticised by the United Nations and other human rights organisations as overcrowded and unfit for humans.
Last month the UN refugee agency UNHCR said conditions at the camp were "reaching boiling point" and urged Greece to speed up transfers of eligible asylum-seekers from Aegean islands to the mainland.
The public health notice warns that all of the problems identified by inspectors must be remedied.
"We are issuing a 30-day deadline," it reads. "Once it expires we will ban its operation over even just one of the aforementioned problems."
A spokesman for the migrant ministry it would speed up efforts to reduce numbers at the camps, adding: "We expect to see results soon."
Lesbos was the preferred entry point into the European Union in 2015 for nearly a million Syrians, Afghans and Iraqis.
Two years ago more than 70 refugees were injured during violent clashes after a fire swept through the camp, destroying tents and shelters.
Migrants detained in Moria while awaiting deportation also said they had resorted to self-harming in the hope of being released more quickly.
Additional reporting by Reuters
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