Two Honduran teenagers who traveled with the migrant caravan to the U.S. border have been killed in Tijuana, authorities said Wednesday, in a stark sign of the risks facing would-be immigrants waiting in Mexican border cities.

Mexican authorities said the bodies of the two boys — thought to be 16 or 17 years old — were discovered last weekend. They had stab wounds and had been strangled after an apparent robbery attempt, according to the state police.

Cesar Palencia, director of migrant affairs for the Tijuana municipality, said in an interview that the boys had arrived with the caravan, but he did not know whether they had requested asylum from the U.S. government. 

Mexican police said the two Hondurans, who were not identified, had left a shelter for migrant youths Saturday to visit a sports arena used as a migrant shelter in another part of the city. Two men and a woman have been arrested and charged in the killings, authorities. 

The boys were believed to be the first victims of homicide from the caravan, which crossed Mexico from south to north starting in October. 

Alex Mensing, project coordinator for Pueblo Sin Fronteras, an organization that supported the caravan, said nearly all the unaccompanied children who traveled with the group intended to seek asylum in the United States. 

The Trump administration allows only a limited number of asylum seekers to enter the country each day at official border crossings, a practice known as metering, because U.S. officials says they cannot handle more. That means asylum seekers can remain for weeks or months in Mexican cities near the U.S. border awaiting their turn to have their claims assessed. 

Immigrant rights activists say the cities are not secure places for migrants, especially children, to wait. 

“For these vulnerable individuals, remaining in Mexico should never be considered a safe and viable option,” said Maureen Meyer, director of the Mexico program at the Washington Office on Latin America, a research and advocacy group. 

Palencia, the Tijuana official, said the killing of the Honduran teens was sad but atypical. “I wouldn’t go as far as saying migrants face danger in the city,” he said. 

But homicides have reached a record level this year in Tijuana, topping 2,000 as drug cartels battle over control of the border crossing and the local Mexican drug market. 

The Trump administration is seeking to have Mexico agree to host migrants not just while they await their initial asylum interviews but throughout the entire process — which could take months or longer. 

The number of asylum seekers from Central America reaching the southern U.S. border has soared in recent years. U.S. officials think the majority are fleeing poverty, not persecution. But countries such as Honduras, El Salvador and Guatemala are extremely violent, with deep-rooted gang problems.