An additional 4,000 to 6,000 Haitians were thought to be making their way from Brazil, immigrant advocates in San Diego and Tijuana said, based on estimates from shelters along the Brazil-to-Mexico migration route.

The message to those Haitians from the Obama administration, however, seems clear: Turn around or go elsewhere.

An uptick in deportations might not occur immediately. Removals require the cooperation of and paperwork from the receiving country, and Homeland Security officials said they were still in talks with the Haitian government about the policy shift.

In the meantime, officials said, nearly all Haitians stopped at the border and scheduled for accelerated deportations will be put into detention centers.

Officials clarified, however, that asylum law would continue to apply to newly arriving Haitians. A migrant who feared returning to Haiti because of the threat of persecution or torture would be interviewed to determine whether that fear was credible. If an immigration officer determined it was, the immigrant could apply for asylum.

Haitian immigrants covered by temporary protected status would be unaffected by the change in policy.

Over the summer, the unusual surge in Haitian migrants was accompanied by an equally unusual surge in migrants from more than two dozen other countries, nearly all traveling along the same arduous routes from South America, across as many as 10 borders.

The migratory wave has overwhelmed shelters along the way, particularly in Tijuana, where the shelters have been at or over capacity for much of the past four months, while also struggling with language and cultural barriers. Some migrants, because they were unable to find accommodations or wanted to avoid shelter living, have chosen to sleep on the streets.