The movement of individuals towards the United States using the perilous tropical expanse called the Darién Gap has been halted, albeit temporarily, subsequent to the detention of two ship commanders employed by firms that have a crucial role in transporting migrants to the wilderness.

Ship companies have suspended migration voyages from two towns in northern Colombia, Necoclí and Turbo, to the threshold of the Darién forest, according to the mayor of Necoclí, leading to about 3,000 migrants being stranded in those localities.

The enforcement actions taken by Colombian authorities in the area are anticipated to be closely monitored by U.S. officials: The Biden administration has been urging Colombia for several months to enhance efforts in preventing individuals from utilizing the Darién as a route to the United States.

The maritime route serves as the primary passage into the Darién Gap, a narrow stretch of land connecting South and North America that was seldom traversed in the past but has recently become one of the most significant and active migration routes in the hemisphere.

Approximately a million individuals have crossed the Darién since 2021, as reported by authorities at the destination in Panama, contributing to an immigration crisis in the United States.

The Colombian Navy recently confiscated two vessels owned by the companies Katamaranes and Caribe, which were carrying a total of 151 migrants from Necoclí towards the jungle, as per the Colombian prosecutor’s office.

After determining that the migrants were being transported unlawfully, authorities apprehended the two ship captains and assumed control of both vessels.

The detentions signify a significant change in strategy by Colombian authorities, who had been permitting ship operators for months to openly transfer migrants from Necoclí across the Gulf of Urabá to the communities of Acandí and Capurganá, where individuals access the wilderness.

In an interview conducted on Wednesday, the mayor of Necoclí, Guillermo Cardona, mentioned that the ship companies, operating sizable fleets with numerous captains, had suspended operations in the recent days “as a means of protest” against the arrests.

Ship operators have become vital figures in a migration industry worth millions of dollars that has thrived in northern Colombia.

In September, The New York Times published a report indicating that this industry was being managed by local politicians and business moguls, including the supervisor of Katamaranes, who was a candidate for mayor in Necoclí back then. (The supervisor did not win, and was not among those detained.)

U.S. officials have been discreetly urging Colombian authorities since at least October to examine the activities of the ship operators.

In a recent dialogue, a senior Colombian prosecutor, Hugo Tovar, disclosed that his office was collaborating “closely” with the United States on the matter of human trafficking through Colombia and the Darién. He added that two U.S. agencies, Homeland Security and Immigration and Customs Enforcement, were offering training and exchanging information to assist in the investigations.

Necoclí, a coastal town with limited resources and infrastructure, has been overwhelmed by migrants in recent years.

The duration of the suspension of operations by the ship companies remains uncertain. If the protest persists, the number of individuals stranded in makeshift shelters on the beaches of the town is likely to rapidly increase, putting considerable strain on water and sanitation services.

This situation could compel the Colombian government to relax any forthcoming arrests of ship operators, considering the government’s limited capability to offer aid to a large number of individuals who might find themselves stuck at its northern border.

Nevertheless, Mr. Tovar emphasized that his office was steadfast in its commitment to combating human trafficking, labeling it “an issue that concerns the entire hemisphere.”

Mr. Cardona, the mayor, appealed to the national government for assistance for the hundreds of migrants who are now stranded without a destination. “This is an SOS,” he remarked.

Migration through the Darién has posed a monumental challenge for the Biden administration, particularly with the approach of the 2024 presidential election.

Both President Biden and his likely Republican contender, Donald J. Trump, are scheduled to appear on Thursday in different areas of Texas near the southern border.

In 2021, slightly over 130,000 individuals traversed the Darién jungle en route to the United States. In 2022, nearly 250,000 did. Last year, in excess of 500,000 individuals crossed the Darién, contributing to a surge in arrivals at the U.S. border.

Mr. Biden has attempted to dissuade this influx by broadening lawful pathways to migration and intensifying deportation efforts at the border.

Nevertheless, these actions have yielded only limited results.

By Feb. 28, authorities in Panama reported that more than 72,000 individuals had journeyed through the Darién this year—marking a 35 percent upsurge compared to the number of individuals who crossed in the initial two months of last year.

The largest contingent of migrants hailed from Venezuela, where hopes among activists for a democratic election under the authoritarian regime have dwindled in recent months. The second largest group arrived from Ecuador, where a grave security situation has worsened this year. The subsequent major contributors in terms of origin are Haiti, Colombia, and China.