Cuban migrants without papers have been ordered out of Panama after withdrawal of automatic entry policy.
"They have to get out of Panama" or risk being deported, Javier Carrillo, the head of Panama's migration service, told AFP.
President Barack Obama on Thursday announced that he was scrapping a 1995 policy known as "wet foot, dry foot" that allowed Cubans without visas automatic entry into the United States if they set foot on US soil.
Those intercepted at sea were sent back to Cuba under the policy, which made passage by land through Central America and Mexico the preferred route for Cuban migrants.
Carrillo said his service counted fewer than 100 Cubans who were in Panama without visas.
But their numbers could be much higher because many undocumented migrants move clandestinely, attempting to circumvent a ban put in place by Panama last year.
The Panamanians acted after Nicaragua shut its border to undocumented migrants, which created a backlog of migrants in countries to its south.
Despite the ban, Cubans migrants are still crossing into Panama from Colombia, traversing the Darien Gap, a swampy, difficult-to-monitor stretch of jungle on the border.
Carrillo said Cubans caught without papers could be sent back to Colombia or to communist-ruled Cuba. He said an agreement was being worked out with Havana to arrange those transfers, he said.
The US move was part of a normalization of ties that Obama agreed with Cuban leader Raul Castro in 2015.
Costa Rica on Friday applauded Obama's decision. The foreign ministry said in a statement it put an end to "preferential" treatment for Cuban migrants that served as a magnet for them to trek through Central America.