Gun battles erupt and vehicles burn in Reynosa, in Tamaulipas state, after arrest of El Gafe, a leader of Gulf Cartel.
Authorities issued an urgent warning residents not to use various main roads because of shooting and blockades.
Social media users posted pictures of burning buses. It was not immediately clear if there were casualties.
Local media said the violence was due to the arrest of a drug cartel leader.
The name El Gafe has started circulating in the local media, though BBC Mexico correspondent Katy Watson says little is known about El Gafe – even his real name.
He is thought to have risen to the top of the Gulf Cartel after the capture and deaths of other leaders.
The US consulate in the city of Matamoros, which oversees consular affairs in Reynosa, urged Americans to “use extreme caution and remain in doors.”
Agencies/Canadajournal