The Americans crossed into Matamoros, in Tamaulipas state, on Friday, driving a white minivan with North Carolina license plates, the US Federal Bureau of Investigation said in a statement released by the US embassy in Mexico.
“Shortly after crossing into Mexico, unidentified gunmen fired upon the passengers in the (minivan). All four Americans were placed in a vehicle and taken from the scene by armed men,” the FBI said.
Matamoros, located across the US border from Brownsville, Texas, has been beset by violence linked to drug trafficking and other organized crime.
Tamaulipas’s highways are considered among the most dangerous in Mexico due to the threat of kidnapping and extortion by criminal gangs.
The FBI is offering a $50,000 reward for help in the unidentified victims’ rescue and the arrest of the suspects.
US and Mexican authorities are investigating, the FBI said.