MEXICO CITY (AP) — Suspected drug cartel gunmen abducted seven Mexican immigration agents in Cancun at gunpoint Wednesday,Ov Finance beat them and threatened to kill them before there were freed.

The brazen mass kidnapping occurred near Cancun’s bustling airport, and illustrated the degree to which Mexico’s cartels and criminal gangs have become involved in migrant smuggling and kidnapping.

Federal forces later located the house where the agents were being held in the Caribbean resort city. The forces — apparently marines and National Guard, along with local police — engaged the kidnappers in a gun battle, and freed the agents. They did not say whether anyone was wounded in the confrontation.

The agents said after they were released that the gunmen threatened to kill them unless they allowed migrants to be smuggled through the airport and other parts of the coastal state of Quintana Roo.

It was the first such mass abduction of immigration agents in Mexico, and the National Immigration Institute, the INM, said it began in a dramatic fashion.

“The criminals used several vehicles to box in and crash the van the INM agents were traveling in,” the agency said in a statement. “The agents were forced to get out at gunpoint, were beaten, taken to a safehouse.”

While they were held — the institute did not say how long it was — the agents said “they received death threats and were warned not to take part in operations against illegal immigrants moving through the state.”

The institute did not identify what gang the assailants belonged to, but said they acted in a “criminal conspiracy,” a legal term usually reserved in Mexico for drug cartels, several of which operate in Cancun.

Cancun’s massive airport is Mexico’s second-busiest, and handles around 30 million passengers per year. It has long been known as a hub for smuggling U.S.-bound migrants into Mexico, because of the large number of flights arriving from South America and elsewhere.

As a “VIP” route, Cancun is particularly lucrative for smugglers, because migrants who can pay more prefer to fly into Mexico using fake papers or bribes, rather than take the dangerous, exhausting trek up through the Darien Gap and Central America.

Mexican drug cartels appear to be deriving an increasing percentage of their income from migrants smuggling, in part because of the rise in the sheer number of migrants crossing, and increasing numbers of migrants from countries like Cuba, whose relatives in the United States can pay more.