NOGALES, ARIZONA — The US Customs and Border Protection Agency has quietly resumed late-night deportation of Mexican citizens, according to human rights activists, despite a 2016 agreement with the Mexican government that halted the controversial practice that makes deportees vulnerable to gangs and human trafficking.

Human rights activists in Nogales said they first noticed the shift in policy in the last week, when US officials deported Mexican nationals at 11 p.m., 11:30 p.m., and midnight, all of which would violate the agreement, which limits deportations to between the hours of 5 a.m. and 10 p.m.

Between 10 and 15 individuals were deported at the later times, according to activists, who said they were sent through the pedestrian walkway, rather than being handed over to Mexican officials, which also appears to violate long-standing practice.

Although the unannounced change in policy may seem minor, it can have life and death consequences for the deported, and appears to be part of a broader effort by the Trump administration to infuse a deterrent effect into the interactions immigrants, both legal and undocumented, have with CBP and Immigration and Customs Enforcement agents.

Neither CBP nor ICE responded to a request for comment.