SARAJEVO, Bosnia (AP) — Croatia launched an investigation Thursday into new allegations that members of its police carry out systematic violent pushbacks of migrants and asylum-seekers attempting to illegally enter the country from neighboring Bosnia.

The announcement came a day after video footage was published of uniformed men in balaclavas beating groups of migrants at a porous segment of the European Union member country’s 1,000-kilometre (620-mile) border with Bosnia.

The footage was filmed during an 8-month long collaborative investigation between journalists at different European news organizations, spearheaded by the non-profit group Lighthouse Reports. Participants included journalists from German ARD public broadcaster and Der Spiegel news website, French Liberation daily and the Swiss SRF broadcaster.

Klaas Van Dijken of Lighthouse Reports told the Associated Press in a telephone interview Thursday that from February to September this year, reporters filmed 11 alleged pushbacks in Croatia, including drone footage of a police officer covering his face with a balaclava before forcing at least 15 people over the border to Bosnia.

Van Dijken said reporters were told by Croatian whistleblowers that “these actions were part of a national operation codenamed Corridor.” The men in balaclavas filmed beating migrants had standard Croatian police issue batons but wore no nametags or police badges on their uniforms.

“Forensic examination of the video revealed that the men had equipment and uniforms consistent with a branch of the Croatian police called Intervention Police,” Van Dijken added.

Human rights organizations have for years been accusing Croatia’s police of brutality and illegal pushbacks of migrants to Bosnia, which Croatia has consistently denied.

Bosnia, which has still not fully recovered from its brutal 1992-95 war, became a bottleneck for thousands of Europe-bound migrants from the Middle East, Central Asia and North Africa several years ago when other nations closed their borders to block migration paths through the Balkans.

Upon entering Bosnia, most migrants walk northwest to the border with Croatia, one of the last gateways to central and northern Europe.

Croatian Interior Minister Davor Bozinovic said Thursday the police had already set up a “special investigative team” to look into the most recent allegations and accompanying video footage.

“The team is already in the field and has a task to establish what happened, where it happened and who took part in it,” Bozinovic said, adding: “there are many questions to be answered.”

Croatian authorities have announced similar investigations in the past, but said they revealed no sign of organized wrongdoing by police

The EU's top migration official, Home Affairs Commissioner Ylva Johansson said Thursday that some of the reports on alleged violence against migrants by Croatian police were “shocking,” and she was “extremely concerned.”

“This needs to be investigated, but they seem to indicate some kind of orchestration of violence at our external borders,” Johansson said.

Follow AP’s global migration coverage at https://apnews.com/hub/migration