The U.S. government kept a database of journalists and activists who were associated with covering or raising awareness of one of the so-called migrant caravans last year, according to documents reviewed by NBC 7 San Diego.

The story of a caravan of thousands of migrants from Central America quickly made headlines last year and drew the attention of President Trump, who campaigned heavily on immigration issues ahead of the 2018 midterm elections.

NBC 7 San Diego reported Wednesday that the journalists and activists who accompanied or monitored the caravan also were tracked by Customs and Border Protection (CBP) and, in some instances, had alerts placed on their passports.

That list, titled "San Diego Sector Foreign Operations Branch: Migrant Caravan FY-2019 Suspected Organizers, Coordinators, Instigators, and Media," reportedly is comprised of 59 individuals, many of whom are American citizens, according to NBC. It reportedly was created so border agents could stop and question specific people when they crossed the southern border.

NBC News further reported that at least 21 individuals in the database were arrested or questioned. It is not clear what, if any, charges were involved.

The list reportedly contains 10 journalists, seven of whom are Americans, an attorney, and others labeled as organizers and instigators. The list shows different symbols based on who was questioned or arrested, with green and red "X" marks used to identify them, NBC reported.

Some individuals had additional information gathered on them by CBP with the help of Mexican officials, according to the report.

The database and documents relating to it were leaked to NBC 7 San Diego by an unnamed Homeland Security source.

CBP appeared to acknowledge the list to NBC News, saying it was made up of people who were present during a violent incident that took place at the border in November and remains under investigation.

A spokesperson for CBP said "criminal events" such as those "involving assaults on law enforcement and a risk to public safety" are routinely monitored by authorities.

"Criminal events, such as the breach of the border wall in San Diego, involving assaults on law enforcement and a risk to public safety, are routinely monitored and investigated by authorities," the spokesperson said.

"These activities could result in a more thorough review of those seeking entrance into our country," the spokesperson added. It is protocol following these incidents to collect evidence that might be needed for future legal actions and to determine if the event was orchestrated."

Updated 9:43 p.m.