In some cases authorities flagged their passports for alerts, the San Diego, California affiliate of NBC reported.

It cited documents leaked to it by a source in the Department of Homeland Security who requested not to be named.

It said these documents list people who officials thought must be screened at the US-Mexico border.

They included 10 journalists, seven of them US citizens, an American lawyer and 47 people from the US and other countries who were labelled as organizers, instigators or with “unknown” roles.

The target list includes advocates from organizations such as Border Angels and Pueblo Sin Fronteras, said the affiliate, NBC 7.

In addition to flagging the individuals for extra screenings, the Homeland Security said agents also created dossiers on each person listed.

“We are a criminal investigation agency, we’re not an intelligence agency,” the source said, according to NBC 7.

"We can’t create dossiers on people and they’re creating dossiers. This is an abuse of the Border Search Authority."

NBC 7 said a Customs and Border Protection spokesperson declined to confirm or deny the validity of the documents.

The spokesperson said in an email that after incidents like breaches of the border wall in San Diego or violence against border agents it is routine to collect evidence for possible future legal action and to determine if such acts were pre-meditated.

"CBP and our law enforcement partners evaluate these incidents, follow all leads garnered from information collected, conduct interviews and investigations, in preparation for, and often to prevent future incidents that could cause further harm to the public, our agents, and our economy," the statement said.