The United Nations warned on Thursday of an “unfolding humanitarian emergency” in Papua New Guinea, as hundreds of asylum seekers barricaded themselves inside an abandoned detention center on Manus Island, choosing to remain inside a camp devoid of food and clean water rather than relocate to alternative facilities in a city nearby.

The camp officially closed on Tuesday, but the detainees have refused to relocate to temporary accommodations, claiming fears of violent reprisals by the island’s residents.

Who are the detainees?

By law, Australia will not resettle any migrants who approach the country by boat, a policy intended to discourage dangerous ocean crossings and human smuggling. Since 2013, Australia has paid Papua New Guinea, its closest neighbor, to house hundreds of migrants caught at sea while trying to reach the continent.

About 600 migrants, all men, and mostly from the Middle East and Southeast Asia, remain at the center. Most of them have sought status as refugees or asylum seekers.