"There are no Ebola cases anywhere in Liberia as we speak," Deputy Health Minister Tolbert Nyenswah told The Associated Press.
In an interview earlier with state media, he said the four patients had recovered and would be discharged in a ceremony on Monday.
"It is still too early to say is it is over," Nyenswah cautioned in the interview, noting that 123 contacts were being monitored.
The cases originated in Nedowein, a community about 30 miles (48 kilometers) southeast of the capital, Monrovia. Samples taken from the 17-year-old boy show the virus is genetically similar to viruses that infected many people in the same area more than six months ago, the World Health Organization has said.