MATAMOROS (ValleyCentral) – Gunmen kidnapped four U.S. citizens in Matamoros who had gone to Mexico to buy medicine and then got caught in a shootout.

The shooting happened Friday afternoon.

Mexican President Andrés Manuel López Obrador said Monday the four traveled to Mexico with the plans to buy medicine but ended up in the crossfire between two armed groups, without offering details.

U.S. Ambassador to Mexico said in a statement the Americans were kidnapped at gunpoint.

“We have no higher priority than the safety of our citizens. This is the most fundamental role of the US government. Officials from various US law enforcement agencies are working with Mexican authorities at all levels of government to achieve the safe return of our compatriots,” Salazar said.

In a news release Sunday night, the FBI said the Americans crossed into Matamoros in a white minivan with North Carolina license plates.

“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,” Oliver Rich, Special Agent in Charge of the San Antonio FBI office Texas, which includes Brownsville, said in the release.

The FBI would not say which of the three international bridges from Brownsville to Matamoros the Americans crossed.

The FBI is offering a $50,000 reward for the return of the Americans and the arrest of those involved. 

Shootouts in Matamoros on Friday were so bad that the U.S. Consulate issued an alert about the danger and local authorities warned people to shelter in place. It was not immediately clear how the abductions could have been connected to that violence Friday.

Tamaulipas state police said people had been killed and injured Friday, but not how many. The state police said on social media that neither law enforcement nor the military were involved in “two armed incidents between unidentified civilians.”

The State Department’s travel warning for Tamaulipas warns U.S. citizens not to travel to Mexico, but all across the Rio Grande Valley, citizens from both countries cross the international bridges on a daily basis.

In Brownsville, residents have the option of driving or walking across Gateway International Bridge, the Brownsville and Matamoros International Bridge and Veterans International Bridge.

Anyone with information is asked to call the FBI San Antonio office at (210) 225-6741 or visit the agency’s website at https://tips.fbi.gov.

The Associated Press contributed to this report.