Some of the first refugees to be sent from Greek islands to Turkey under a controversial deal struck with the European Union may have been deported by mistake, according to a report.

The allegation was made as Greece postponed deportations until Friday because thousands of the migrants have applied for asylum — rendering them ineligible to be rousted from detention camps.

Greek police “forgot” to process the asylum claims of 13 of the 202 refugees sent to Turkey on Monday, according to Vincent Cochetel, head of the UN High Commission for Refugees’ Europe bureau, The Guardian reported.

“It is more a mistake than anything else — we hope,” he said.

The 13 migrants who arrived on the island of Chios after March 20 had not been allowed to register their asylum claims due to administrative problems before they were deported Monday.

The EU did not say if it will investigate the allegation, which could undermine the EU’s argument that the deal conforms to international law. Chios police denied that anyone had been sent back to Turkey against their will.