A team of American scientists traveled to Colombia to examine the mosquito-borne Zika virus and help develop a vaccine for the disease, said the US ambassador.
The US experts are studying "the possibility of a vaccine" alongside specialists from the Colombian Health Ministry, Ambassador Kevin Whitaker said from Bogota, the capital of the second worst-hit nation.
He said the team would also seek to prove whether Zika definitively causes the severe neurological disorder Guillain-Barre syndrome as well as microcephaly, or abnormally small heads and brains, in babies born to women infected with the disease.
"There is a major concern in my country over what has happened with Zika in Colombia and Latin America."
The researchers from the US Centers for Disease Control and Prevention (CDC) and Colombia's National Health Institute (INS) are partnering to get down to the basic science of the disease.
In Colombia, health officials have reported that three people died due to Guillain-Barre syndrome linked to Zika.
There are more than 25,000 cases of Zika across the country -- 22,600 confirmed cases and around 3,000 suspected cases -- according to the latest INS figures. Of these, 3,000 are pregnant women.
Zika normally causes mild flu-like symptoms and a rash or goes unnoticed altogether.
The United Nations has urged countries hit by the dangerous virus to let women have access to contraception and abortion.
Zika is transmitted by the Aedes aegypti mosquito, which also spreads dengue fever. More than 600,000 cases of Zika are expected in Colombia by the end of the year.