The European Anti-Fraud Office (OLAF) on Monday launched a probe into the European Border and Coast Guard Agency (Frontex) due to the agency's role in the pushback of migrants from Greece to Turkish territorial waters and other charges including harassment and misconduct.

While both OLAF and Frontex confirmed the probe was launched, none of them shared further details.

"OLAF can confirm that it has opened an investigation concerning Frontex," the anti-fraud agency's press office said as reported by news website Politico, stressing: "The fact that OLAF is conducting an investigation does not mean that the persons/entities involved have committed an irregularity/fraud."

In a statement, Frontex said it "is cooperating fully with OLAF," adding that: "OLAF visits to EU agencies, institutions and entities are a normal practice of good governance" and that "it's important to note that such visits do not necessarily imply any malpractice. They may also be triggered by the management of European bodies themselves."

OLAF investigators have been interviewing members of the Warsaw-based agency "since the start of last month," said one of the EU officials, who told Politico on the condition of anonymity.

In early December, EU lawmakers lashed out at Frontex's executive director over allegations that the agency helped illegally stop migrants entering Europe and supported Greek coast guards to push migrants back toward Turkish territorial waters in the Aegean Sea, calling for his resignation and demanding an independent inquiry.

The lawmakers grilled Executive Director Fabrice Leggeri over an investigation in October by several international media outlets, which said video and other publicly available data suggest Frontex "assets were actively involved in one pushback incident at the Greek-Turkish maritime border in the Aegean Sea."

The report said personnel from the agency, which monitors and polices migrant movements around Europe's borders, were present at another incident and "have been in the vicinity of four more since March." Frontex launched an internal probe after the news broke.

Pushbacks are considered contrary to international refugee protection agreements, which say people shouldn't be expelled or returned to a country where their life and safety might be in danger due to their race, religion, nationality, or membership in a social or political group.

While the border agency is required to rescue migrants, the Frontex vessels patrolling the area sped past the overcrowded, inflatable boats, creating dangerous waves to force them to return to Turkish shores. A Frontex aircraft was also documented passing over migrants, who were seeking help at sea, but did not rescue them.

Turkey and Greece have been key transit points for migrants aiming to cross into Europe, fleeing war and persecution to start new lives. Turkey has also accused Greece of large-scale pushbacks and summary deportations without access to asylum procedures, which is a violation of international law. It also accuses the EU of turning a blind eye to what it says is a blatant abuse of human rights.