Eight Cuban migrants and a small Pekingese dog were found by Puerto Rican authorities on an uninhabited island near the US territory.
US Customs and Border Protection said on Thursday that the group landed on Mona Island, west of Puerto Rico. Officials said that a child was part of the group and the federal agency is temporarily caring for the dog.
Cubans are increasingly leaving their island amid fears they might lose a special status that gives Cubans automatic residency in the United States if they reach its soil.
Federal agents have detained more than 150 Cuban migrants in the region so far this fiscal year.
Cubans are concerned that in the aftermath of re-establishing diplomatic relations Washington will cease or change its immigration policies, which will grant Cubans relatively easy visa-free residence.
However, Nicaragua and Ecuador - both allies of Cuba unlike Costa Rica - block the passage of migrants without visas.
A backlog has led many Cuban migrants, who use the countries as a transit point through United States, to be left stranded in Costa Rica.
Costa Rica, where the flow of Cuban migrants has increased nearly 80 percent this year, stopped issuing transit visas to Cubans earlier in December 2015.
There is currently an estimated 8,000 Cubans barred from entering Nicaragua in Costa Rica.
Earlier this month, the US called on Central American governments to find a solution to the humanitarian crisis.
Cuban mass migration to the US first started when communist leader Fidel Castro overthrow the US-backed government of Cuba in 1959 and aligned itself with the Communist USSR.
Cubans who feared of the negative consequences of the political transition then immigrated to the US, mainly during 1960s and 1970s.
In support of those fleeing the communist regime, the US gave Cubans financial assistance and automatic residence with the 1966 Cuban Adjustment Act.
After a half-century estrangement, the United States and Cuba marked a new era in their diplomatic ties by re-opening their embassies in July 2015.