Mexico City (CNN) -- At least 18 people were killed in a shootout in the Mexican border state of Tamaulipas, state media reported.
The state government said the Monday morning shootout was "between organized crime groups," according to the Notimex news agency.
Notimex said the shootout paralyzed the city of Abasolo -- located about 150 miles (240 kilometers) south of McAllen, Texas.
Authorities closed a highway and suspended classes at local schools as the violence erupted in the early morning hours.
Residents told Notimex that the area, once known as a tranquil place, is now plagued by violence in the streets and a spike in vacant homes as the city's inhabitants flee.
A statement from the Tamaulipas government said federal and state authorities were investigating and stepping up their presence in the area, Notimex said.
Tamaulipas has been a battleground in a bloody turf war between the Zetas gang and the Gulf cartel, but authorities did not indicate which drug gangs they believe were involved in Monday's shootout.