A United States Border Patrol agent was involved in a shooting in Arizona, Pima County Sheriff Chris Nanos said in a statement on Tuesday, adding that his office was working with the FBI and Customs and Border Protection to look into the incident.

The Santa Rita Fire District said one person was in critical condition. CNN, citing a federal law enforcement source, reported the wounded person was a suspect who had exchanged gunfire with Border Patrol agents and fired at a federal helicopter during a pursuit near the border.

The FBI said it was investigating an alleged assault on a federal officer near the town of Arivaca in Arizona, about 10 miles from the US-Mexico border, and that a subject was taken into custody, adding that the investigation remains ongoing.

The Santa Rita Fire District and American Medical Response provided medical care to the individual who was shot on the scene before transporting them in critical care for further treatment, NBC News reported.

Person shot not identified

The circumstances of the incident were not immediately clear, and the person who was shot has not been identified. The Department of Homeland Security did not immediately respond to a Reuters request for comment.

Nanos said the FBI requested assistance in the investigation of the shooting, adding that the Pima County Sheriff's Department Criminal Investigation Division would conduct a parallel investigation and had been asked to lead the use-of-force investigation involving the Border Patrol agent.

"We ask the community to remain patient and understanding as this investigation moves forward. PCSD will thoroughly examine all aspects of the incident; however, these investigations are complex and require time," Nanos said.

This is a developing story.