The rise in Haitian migration began in the months after President Biden took office and quickly began reversing former President Donald J. Trump’s strictest immigration policies, which was interpreted by many as a sign that the United States would be more welcoming to migrants. In May, the administration extended temporary protected status for the 150,000 Haitians already living in the country. But tens of thousands have attempted to cross into the United States since then despite not qualifying for the program.

“False information, misinformation and misunderstanding might have created a false sense of hope,” said Guerline M. Jozef, the executive director of the Haitian Bridge Alliance, an organization that works with migrants.

Mr. Biden’s term has coincided with a sharp deterioration in the political and economic stability of Haiti, leaving parts of its capital under the control of gangs and forcing tens of thousands to flee their homes. The assassination of Haiti’s president and a magnitude 7.2 earthquake this summer have only added to the pressures causing people to leave the country. Shortly after the assassination, hundreds of Haitians flocked to the U.S. Embassy in Port-au-Prince, many carrying packed suitcases and small children, after false rumors spread on social media that the Biden administration was handing out humanitarian visas to Haitians in need.