According to Sunday reports, gunmen in sports utility cars shot about fourteen individuals in the various districts of Reynosa Mexican border city.
Someone in a police attack at the border bridge was allegedly murdered.
Over the border from McAllen, Texas, criminal activity in the city has been dominated by the Golf Cartell for many years, but divisions in the Gang are believed to have formed.
The death toll reached 18 on Sunday in local media reporting.
According to the Tamaulipas State Agency that organizes security forces, the attacks started early Saturday afternoon in different communities in the eastern portion of Reynosa.
Originally, the identity of the victims and the perpetrators and the reason was unknown.
'Investigations have been launched with a view to identifying the causes of homicides and locating the perpetrators, in particular for monitoring and patrol actions in various districts of Reynosa," a report said.
The military, National Guard, the police in the state, and other authorities have been mobilized by violence.
Deaths spiraling in the fight for power
Mexico's two bloodiest years, 34,681 in 2019 and 34,554 in 2020, have been recorded.
Different cartels struggle to control the smuggling of the drug, gun, and human trafficking routes into the US.
Successive governments failed to tame the criminal unions. Many have accused the police and the judiciary of having colluded with the gangs and of succeeding in corruption for wholesale.
Spiraling figures on homicides, instability, and high levels of bribery have led some American critics to say that Mexico is on its way to being a failed country.
The current president, Andres Manuel Lopez Obrador, said that he wanted "hugs and no bullets" to battle cartels.
For his measures which prioritized the elimination of the cartel bosses, Lopez Obrador attacked earlier administrations.
US Secretary of Homeland Security Alejandro Mayorkas refused to judge the policy, saying that he didn't actually know what it meant.