ATHENS – A group of United Nations experts on arbitrary detention said Friday that despite some improvements, Greece was still in violation of certain international obligations in how and where people are imprisoned.

The U.N. Working Group on Arbitrary Detention presented a preliminary report following a visit to 20 detention facilities across the country between Dec. 2 and Dec. 13. It noted several areas of concern involving both the criminal justice system and migration.

A final report will be be issued in several months. The group, which visited Greece following an invitation by the 6-month-old government, said it had enjoyed unrestricted access to facilities and full cooperation from Greek officials.

The group’s concerns included prison overcrowding, the non-segregation of suspects held in pre-trial detention from those already convicted, the access of asylum seekers to interpreters and legal help, and reports of arbitrary push-backs into Turkey of migrants attempting to cross the border into Greece.

Greek prisons have suffered from overcrowding for years. A recent change to the penal code reducing the length of prison sentences and encouraging the use of alternatives such as community service “are positive steps forward,” the group said. But it added that “there is still considerable scope for their implementation,” and noted that the conditions in prisons and police station holding cells “do not generally meet international standards.”

The preliminary findings criticized the widespread use of pre-trial detention. It also said that holding people awaiting trial together with convicts runs contrary to the International Covenant on Civil and Political Rights and is “contrary to the presumption of innocence that all persons are entitled to prior to conviction.”

Regarding push-backs, the group said it had received information from various sources, including lawyers and non-governmental groups, that some migrants attempting to enter Greece from Turkey “are arrested, detained in very poor conditions, and summarily returned across the Greece-Turkey land border” without being given the chance to apply for asylum.

“We understand that it’s not occasional. In fact, we understand that it’s a long-standing practice dating back several years now,” said Leigh Toomey, vice chair of the group. Toomey said the group was currently “in dialogue” with the government regarding the reports, and did not have information on how many people were believed to have been the subject of push-backs.

This was the second visit by the UN’s Working Group of Arbitrary Detention to Greece. The first was conducted in 2013.