The fires have destroyed Greece’s largest migrant camp, an overcrowded facility on the island of Lesbos, leaving nearly 13,000 people without shelter.
About 20 firefighters extinguished the blaze at the Moria camp – designed for fewer than 3,000 people.
Police watch the roads from the camps to prevent migrants from entering nearby towns.
Many tried to bring their goods to the port city of Mytilene but access was closed.
Reports suggest many slept in the fields after the fires.
Home affairs commissioner Ylva Johansson said she had agreed to finance the transfer of 400 unaccompanied teenagers and children to mainland accommodation.
The fire was originally sparked by strong winds, went out on Wednesday morning,
A local resident told the BBC that almost the entire camp was on fire.
Michalis Fratzeskos, deputy mayor for civil protection, told ERT that the blaze was “planned”.
Because the incident occurred when the migrant tents were empty, and the combustion system had “taken advantage of the strong winds”.
Several migrants told BBC Persian that the fires broke out after clashes between migrants and Greek troops at the camp.