Carla Provost, chief of the US Border Patrol, participated in a secret Facebook group used by members of her agency to share racist and violent commentary about migrants, a report has alleged.

Ms Provost addressed the group and its controversial content, which was posted by current and former Border Patrol officers, when it was uncovered earlier this month.

In a public statement at the time, she said: “These posts are completely inappropriate and contrary to the honour and integrity I see — and expect — from out agents day in and day out.