Several Border Patrol agents used undue force against Haitian migrants along the southwest border last fall, but there was “no evidence” that any agents on horseback struck them with reins, investigators found in a report.

U.S. Customs and Border Protection’s Office of Professional Responsibility released the 511-page final report Friday, more than nine months after viral images of border agents on horses using reins against migrants in south Texas sparked outrage in Congress and nationwide.

The images were released amid a sharp rise in migration from Haitian citizens in Texas’ Del Rio sector, resulting in as many as 15,000 migrants crowded under the international bridge at once in dangerously high temperatures.

The report found that Border Patrol agents involved had not been given sufficient training or briefed on the agency’s objectives when they decided to help Texas state officials push back Haitian migrants crossing the Rio Grande River. Several of the migrants had been issued tickets by Border Patrol indicating they were already awaiting processing by the agency, but they had crossed back and forth for supplies for their families.

One agent “used profanity while yelling at a migrant and then pursued him along the river’s edge forcing his horse to narrowly maneuver around a small child,” the report says. Multiple agents on horseback “used force or the threat of force to drive migrants back into the Rio Grande River despite the fact they were well within the territorial boundary of the United States,” according to the report.

The horseback agents were equipped with split reins, which one agent reported twirling as a distancing tactic. But the report says there was “no evidence that [Border Patrol agents] involved in this incident struck, intentionally or otherwise, any migrant with their reins.”

CBP Commissioner Chris Magnus told reporters Friday that the agency had convened a Discipline Review Board that proposed disciplinary measures against four agents, but he declined to elaborate further while the disciplinary process is ongoing.

“Not everyone’s going to like all the findings, but the investigation was comprehensive and fair,” Magnus said at a news conference.

The long-anticipated report follows widespread outcry of Border Patrol agents’ actions among the public and on Capitol Hill.

Homeland Security Secretary Alejandro Mayorkas told lawmakers in September that he was “horrified” by the viral images of Border Patrol agents confronting migrants and pledged an investigation. Vice President Kamala Harris, congressional leadership and members of the Congressional Black Caucus also spoke out against the images and treatment of Haitian migrants.

Mayorkas announced in late September that the migrant encampment under the Del Rio bridge had been cleared out, after a month that saw 30,000 migrants, mostly from Haiti, crossing the southwest border in that area.

Caroline Simon contributed to this report.