ATHENS — The European Union's border patrol Frontex agency, which scouts land and sea territories, said it couldn't find any proof to claims by activists and media reports that Greece deliberately pushed back refugees and migrants.

Frontex assists the Greek Coast Guard that patrols the Aegean and East Mediterranean but haven't been able to keep scores of thousands of refugees and migrants reaching Greek islands near Turkey or crossing the land border.

Turkey is holding some 4.4 million refugees and migrants who went there fleeing war and strife in their homelands, especially Syria and Afghanistan, and also economic misery in Sub-Saharan Africa and other countries.

But Turkey has allowed human traffickers to keep sending more during an essentially-suspended 2016 swap deal with the European Union which has closed its borders to them, other countries also reneging on promises to help take some of the overload.

Frontex's Executive Director Fabrice Leggeri said the agency couldn't find evidence to back up claims in international media reports, by Turkey as well as other groups that Greece pushed back boats and dinghies carrying refugees and migrants toward Greek islands.

In the same letter, which Kathimerini said it had see, he asked for an “in-depth analysis” of EU regulations, especially those concerning orders issued to smuggling vessels to leave the territorial waters of a member state or to stop heading toward them.

Frontex late in October began the internal inquiry after media reports suggested that it was complicit in illegal pushbacks aimed at preventing migrants and refugees from entering Europe through the Greek islands.

Media outlet Bellingcat reported that video and other data suggest Frontex "assets were actively involved in one pushback incident at the Greek-Turkish maritime border in the Aegean Sea, were present at another and have been in the vicinity of four more since March."

Bellingcat said that while Frontex was not present at the other four incidents, "the signature of a pushback is distinctive, and would likely have been visible on radar, with visual tools common on such vessels or to the naked eye."

Its findings were part of a joint investigation with Lighthouse Reports, Der Spiegel, ARD and TV Asahi.

"We are looking into the accusations levelled by several news organizations related to our activities at Greece's external borders," Leggeri said then in a statement. He said that the EU agency does "not tolerate any violations of the fundamental rights in any of our activities."

"So far, no documents or other materials have been found to substantiate any accusations of violations of the law or the Frontex Code of Conduct by deployed officers," Leggeri said. The media outlets said their investigation was based on open source data, including Turkish coast guard video imagery.

Pushbacks are considered contrary to international refugee protection agreements. Under the principle of "non-refoulement," people should not be expelled or returned a country where their life and safety might be in danger due to their race, religion, nationality or being members of a social or political group.

Frontex said that its work in the eastern Aegean has been complicated by a dispute between Turkey and Greece over maritime borders. Greek and Turkish coast guard ships are routinely involved in standoffs and threats in the narrow stretch of water that separates the two countries.