Liberia closed its border with Guinea on Tuesday as a precaution against Ebola following at least four deaths from the virus in Guinea, Information Minister Lenn Eugene Nagbe said.
The deaths have occurred since Feb. 29, while Liberia was declared free of new transmissions of the virus in January.
"We are not taking any chance at all."
A team of medics with protective gear had been sent to the border to improve surveillance.
Ebola, a haemorrhagic fever, has killed about 11,300 people in the two countries plus Sierra Leone since late 2013 and it caused global alarm in 2014 as governments and health agencies rushed to help contain the outbreak.
New cases have dwindled virtually to zero but the U.N. World Health Organization has warned of flare-ups, or emerging clusters, of new cases.