Search underway for Americans kidnapped in Mexico

STORY: Mexican and U.S. authorities said on Monday that they were searching for four Americans who were kidnapped in northern Mexico after being shot at by gunmen and thrown into the back of a pickup truck shortly after crossing the southern border.

The U.S. Embassy in Mexico said the four unidentified Americans – three men and one woman – were in a white minivan with North Carolina license plates when they entered Matamoros on Friday – a city just over the border from Brownsville, Texas.

Mexican president Andres Manuel Lopez Obrador said the public security ministry was working with the FBI to locate the missing Americans.

"According to the information we have, the U.S. citizens crossed the border to shop for medication in Mexico. There was a confrontation between groups, and they were detained.”

The White House said it was closely following the situation.

"These sorts of attacks are unacceptable. Our thoughts are with the families of these individuals, and we stand ready to provide all appropriate consular assistance. U.S. law enforcement is in touch with Mexican law enforcement. The Departments of State and Homeland Security are also coordinating with Mexican authorities, and we will continue to coordinate with Mexico and push them to bring those responsible to justice."

The U.S. State Department has advised Americans not to travel to Matamoros, in part due to the threat of kidnapping.

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