Greece officials said Tuesday they are temporarily halting the forced deportation of refugees after an overwhelming number of people being held in migrant detention camps submitted applications for asylum.

The announced came amid warnings from the United Nations' refugee agency that the EU member nation may have "mistakenly" sent asylum-seekers back to Turkey without processing their claims, which would be a violation of international law.

Vincent Cochetel, director of the UN's High Commission for Refugees (UNHCR) bureau in Europe, told the Guardian that 13 Afghan and Congolese people who were among the first wave of refugees sent back to Turkey on Monday had not been allowed to formally register their asylum claims, contradicting statements made by EU officials that all of the people returned so far under the contentious EU-Turkey agreement had done so "voluntarily."

"For four days after the 20th, the Greek police did not register any intention to seek asylum as they were not prepared [or] equipped for this, so [UNHCR] started providing forms to people who had declared their intention to seek asylum," Cochetel said.

"The police received most of the people with these forms and...forgot some apparently," he added. "It is more a mistake than anything else, we hope."

The blunder is the latest strike against a policy that humanitarian organizations have criticized for being inhumane.

The Guardian further reports, "EU officials repeatedly avoided saying whether they will investigate the allegation, which threatens the legitimacy of the deportation deal. If proved, the claims would undermine the EU’s argument that the deal, which could lead to the expulsion of almost all asylum seekers who arrived in Greece after 20 March, is in line with international law."

The agreement stipulates that asylum seekers must be screened before they are deported. According to Maria Stavropoulou, director of Greece's Asylum Service, the application process typically takes about three months to process but would be "considerably faster" for the thousands currently held in detention camps.

Those individuals who have arrived in Greece from Turkey on or after March 20 are eligible for deportation "if they do not apply for asylum or their application is rejected or inadmissible," AP notes. Stavropoulou said Tuesday that more than 3,000 people are now seeking asylum and that the overloaded agency would postpone its next migrant return until Friday.