Four Americans who were abducted last week in northeastern Mexico are being looked for. They were apparently caught up in a gunfight that killed one Mexican.
They were in a white minivan going through Matamoros when people with guns opened fire on them.
Heavy-armed men are seen on video putting them in the back of a pickup truck.
Andrés Manuel López Obrador, the president of Mexico, says that the Americans crossed the border to buy medicine.
But US officials didn’t back up his claim. They haven’t said who the four missing people are.
President López Obrador said that his “whole government” was working to get the four US citizens released.
On Monday, he met with US Ambassador Ken Salazar at Mexico City’s National Palace.
The president said, “There was a fight between two groups, and they were taken.”
Mr. Salazar said that the incident also caused the death of a Mexican citizen who had done nothing wrong.
A video shared on social media shows four people being loaded into the bed of a pickup truck by gunmen in broad daylight. One person is helped into the car, while others, who look like they are unconscious, are dragged to the truck.
CNN quoted an unnamed US official as saying that investigators think a Mexican drug cartel may have thought the Americans were Haitian drug smugglers.
“The safety of our citizens is the most important thing to us,” the ambassador said. “People from different US law enforcement agencies are working with Mexican authorities at all levels of government to get our people back safely.”
Press secretary Karine Jean-Pierre said that the White House was keeping a close eye on the “unacceptable” attack and kidnapping.
“The families of these people are in our thoughts,” she said.
The Mexican government is likely to put finding the Americans at the top of its list in order to avoid a big problem at the border.
Mr. López Obrador said that he had talked to the governor of Tamaulipas about the kidnappings over the weekend.
Mr. López Obrador said, “I think it will be solved.” “I’m hoping that.”
An official in Mexico told the news agency Reuters that three men and one woman had been taken.
The US State Department tells travellers not to go to Tamaulipas and five other states in Mexico because of “crime and kidnapping.”
It is thought to be one of the most dangerous places in Mexico because drug cartels run a lot of it and often have more power than the local police.
The FBI wants the public’s help and is offering a reward of $50,000 (£41,620) for information that leads to the return of the missing US citizens and the arrest of the people who took them.