After media reports about illegal pushbacks of refugees, the Greek authorities are under pressure.
The European Commission is demanding an investigation into what is happening at the border, Commission spokeswoman Anitta Hipper said in Brussels on Tuesday.
However, no further conclusions would be drawn at the moment.
"For now, we're not talking about violations of the law," she said.
Several media had previously reported that Greek police officers were apparently using refugees as henchmen for illegal repatriations at the EU's external border.
German Foreign Minister Annalena Baerbock (Greens) wrote on Twitter that the events and allegations had to be fully clarified.
She referred to the allegations against the Greek government as well as against Spain and Morocco.
At the border to the Spanish exclave of Melilla, more than 20 people died violently over the weekend.
Baerbock explained: "The suffering reminds us that we still have a long way to go in the EU in terms of asylum and migration policy."
As can be seen from the joint research published on Tuesday by the ARD political magazine "report Munich" with the "Spiegel", "Lighthouse Reports", "Le Monde" and the "Guardian", refugees have given corresponding information, which can be verified by means of photos, satellite images and get official Greek documents verified.
After months of research, a team of reporters was able to speak to six men who were involved in the so-called pushbacks.
Independently of one another, they stated that they had been forced into violent refusals to Turkey.
In return, they were promised residence permits.
Three Greek police officers also confirmed the use of refugees to the journalists.
The Greek Ministry of the Interior and the police had left official inquiries about this unanswered by Tuesday.
The Vice-President of the Bundestag, Katrin Göring-Eckardt (Greens), brought up European sanctions against Athens in view of the research.
"Using refugees in need as helpers for illegal pushbacks is deeply inhuman and violates all rule of law," she told the newspapers of the Funke media group.
The EU should not turn a blind eye to Greece's brutal actions.
"An independent investigation is needed and possible sanctions against Greece must also be discussed."
According to European law, Greece is obliged to start an asylum procedure for those seeking protection who reach Greek territory.
Like some other EU countries, the Greek government has been systematically ignoring this regulation for years.