Government investigators are reviewing U.S. Border Patrol policies on use of lethal force amid a spate of deadly shootings along the border in recent years, including the killing last week of a teenager who agents said was throwing rocks at them from across a fence in Mexico.

Since 2010, at least 18 people have been killed by Border Patrol agents, eight in instances where federal authorities said they were being attacked by rock-throwers, a common occurrence along the Mexican border, said Vicki Gaubeca, director of the ACLU’s Regional Center for Border Rights, in Las Cruces, N.M.

The probe by the Department of Homeland Security’s Office of Inspector General involves a review of accusations of brutality and excessive force as it works to determine whether reforms have been implemented.

The review, briefly referenced in a 100-page report released this month, was launched after 16 members of Congress expressed concern over the 2010 death of an unarmed Mexican migrant in San Diego. They asked the Department of Homeland Security to determine whether the incident is “emblematic of a broader cultural problem” within the agency.

“It is ongoing,” Arlen Morales, a spokeswoman for the Inspector General’s Office, said Thursday.