Eleven congressmen have sent a letter urging a nonpartisan government watchdog to audit the U.S. Border Patrol's activities on the northern border.

Led by Democratic Rep. Hansen Clarke of Michigan, the Democratic lawmakers want the U.S. Government Accountability Office to investigate if Border Patrol agents are violating civil rights, undermining immigrant communities and adversely affecting public safety.

Immigrant rights groups said Tuesday the letter was prompted by reports of agents targeting individuals based on appearances on the northern border.

An email seeking comment to the Border Patrol was not immediately returned.

But in previous instances, the agency has denied targeting people based on race.

Advocates say they have not heard from the Government Accountability Office if they will undertake an audit.

The letter was sent late July.