Can the Federal Protective Service make arrests without identification or in unmarked cars?

This week, a protestor who was part of the George Floyd protests in Portland, Oregon was arrested by federal agents who were without identification, and who put him into an unmarked van. Customs and Border Protection (CBP) issued a statement that these were CBP agents that were deputized as officers of the Federal Protective Service (FPS) and were arresting the protestor on suspicion that he attacked federal property or federal employees.

This made me curious about two things. First of all, do FPS officers have the authority to make arrests without having uniforms that identify themselves as being FPS officers? Second of all, when they do make arrests do they have the authority to put the arrested persons into unmarked cars?

Do either the US Code or the Code of Federal Regulations discuss this issue?