Some U.S. border agents have started wearing body cameras in a test of the technology in the field.

U.S. Border Patrol Assistant Chief Donna Twyford said Friday roughly three dozen cameras are being worn by personnel on a volunteer basis during a 90-day test period at locations in New Mexico, Texas, Florida, Michigan and Washington state.

Twyford says the test will help Customs and Border Protection determine whether cameras can be used in the field.

Authorities previously tried out the cameras at academies where border agents are trained.

The agency tasked with manning the country's borders, ports and airports announced the plan to test out cameras after fielding complaints about the use of force.

Union officials have raised concerns about how the cameras may be used.