Those making their way across the border are likely involved with smuggling and storage of drugs, authorities said. They are also likely to keep a low profile ....
The Zetas and Gulf Cartel have an ongoing power struggle to control Matamoros (just across the Rio Grande River from Brownsville). Firefights between the groups happen often and have left many casualties.
Officials don’t believe the organizations would allow their gun battles to cross the Mexican border to the United States — at least they hope not.
"I think they have to be careful that they are not causing problems here," said Brownsville Police Chief Carlos Garcia. "If they are causing problems on the Mexican side and then they cause problems on this side, where are they going to run after that? Where are they going to hide?""