FBI searching for four US citizens kidnapped after crossing border into Mexico

Four U.S. citizens were kidnapped after crossing the border from Texas into Mexico, federal authorities said Sunday in a plea for help from the public.

The victims, who have not yet been identified, were traveling in a white minivan with North Carolina license plates on Friday when they crossed the border into the city of Matamoros, which is located in the northeastern state of Tamaulipas and home to warring factions of the Gulf drug cartel.

"Shortly after crossing into Mexico, unidentified gunmen shot the passengers of the vehicle," a statement from the U.S. Embassy in Mexico City read. "The gunmen herded the four U.S. citizens into another vehicle and fled the scene with them."

The Mexican city, which is just south of Brownsville, Texas, had been plagued by shootouts in recent days, leading the U.S. Consulate to issue a warning about the danger on Friday.

State police in Tamaulipas said people had been killed and injured Friday but did provide any numbers, according to the Associated Press.