FBI offers $50,000 reward after four Americans abducted by armed men after crossing into border city of Matamoros.

The Federal Bureau of Investigation (FBI) said in a statement that the four Americans crossed the border into Matamoros, in Mexico’s northeastern state of Tamaulipas, on Friday in a white minivan.

“Shortly after crossing into Mexico, unidentified gunmen fired upon the passengers in the vehicle. All four Americans were placed in a vehicle and taken from the scene by armed men,” the statement said.

Matamoros, a city across from Brownsville, Texas, has been beset by violence linked to drug trafficking and other organised crime.

Highways in the Mexican state are considered among the most dangerous in the country due to the threat of kidnapping and extortion by criminal gangs.

On Friday, shootouts in Matamoros were so bad that the US consulate issued an alert about the danger and local authorities warned people to shelter in place.

Tamaulipas state police said people had been killed and injured, but did not say how many. The state police said neither police nor the military was involved in the shootouts.

“There have been two armed incidents between unidentified civilians,” they said on Friday on social media. “The exact number of the fallen is being corroborated.”

Meanwhile, the FBI said in its statement that US and Mexican law enforcement agencies were investigating the abductions of the four Americans.

The FBI also offered a $50,000 reward “for the return of the victims and the arrest of those involved”.