The content originally appeared on: Al Jazeera – Latin America News

Authorities in the United States and Mexico have said they are working to secure the release of four US citizens who were fired upon and kidnapped in a northern Mexican border city.

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 with North Carolina licence plates.

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

A Mexican official told the Reuters news agency that three men and one woman were kidnapped.

“An innocent Mexican citizen was tragically killed” in the incident, US Ambassador to Mexico Ken Salazar said in a statement on Monday, adding that US law enforcement agencies were working with their Mexican counterparts “to secure the safe return of our compatriots”.

Mexican President Andres Manuel Lopez Obrador said that the victims were believed to have entered the country to buy medicines and got caught up in a confrontation between criminal groups. He did not offer additional details.

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

Highways in Tamaulipas 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”.

During a news conference on Monday afternoon, White House Press Secretary Karine Jean-Pierre said the US Department of State and the Department of Homeland Security also were coordinating with the Mexican authorities on the case.

“These sorts of attacks are unacceptable,” Jean-Pierre told reporters. “Our thoughts are with the families of these individuals and we stand ready to provide all appropriate consular assistance.”