A Border Patrol agent was assaulted while arresting an illegal migrant in Arizona's Tucson Sector of the border, officials said.

The incident occurred at about 4 a.m. Saturday, Customs and Border Protection wrote in a statement. 

"While being placed in a service vehicle, the subject assaulted the agent, injuring the agent's face and hands. Additional agents responded and took the suspect into custody," officials said.

The injured officer was taken for medical treatment. The assault is being investigated by the FBI and the Cochise County Sheriff's Office. 

The officer's identity was not immediately clear, but sources familiar with the matter told Fox News that the assaulted officer was a woman.