Unexploded bombs have been found in a new refugee camp on the Greek island of Lesbos.
The Human Rights Watch (HRW) said residents discovered bombs, machine gun ammunition and machine gun shells on the site, which is a former Greek military firing range.
The settlement was hastily constructed in September after the nearby Moria camp burnt to the ground, making an estimated 13,000 refugees homeless.
The government had claimed the Kara Tepe site was cleared of military debris before refugees moved there.
HRW, however, claims authorities failed to conduct lead testing of soil remediation before moving refugees to the site.
The rights watchdog warned residents could be at risk of lead poisoning.
HRW's senior crisis and conflict researcher Belkis Wille said: "Putting thousands of migrant adults and children, along with aid workers, on top of a former firing range without taking the necessary steps to guarantee they would not be exposed to toxic lead is unconscionable."
The rights watchdog has called on the Greek authorities to conduct an assessment of the site's soil lead levels and publish the results.
Greek Defence Ministry officials said ordnance crews had cleared the site and surveyed its ground for poisonous metal when the camp was built, the Timesreported.
However, the results of the surveys have not yet been released.
Refugees told HRW their children no longer played around the camp for fear of accidents involving firing debris.
"We try to stop our children from going to play up the hill because we know there might be bullets and other things the army didn't clear that could be dangerous," one said.
The latest report adds to growing condemnation of Greece's handling of the migration crisis.
Over 100,000 refugees remain stranded in Greece, four years after a wave of mass migration reached Europe's borders.
European Union (EU) leaders called for 'No more Morias' following the devastating fire in September.
However, in October Greek authorities announced plans to build a permanent Moria camp replacement on Lesbos by summer 2021.
Permanent camps will also be built on the islands of Samos, Kos and Leros, Migration Minister Notis Mitarachi said.
The camps will be closed facilities with tightly controlled entry and exit systems, as well as fire protection systems.
HRW has criticised these plans, warning European leaders against perpetuating Greece's containment policy of blocking transfers of refugees to the mainland.
The report calls on the EU and Greece to "fundamentally reconsider" their approach to refugees on the Greek islands.