Liberia has placed 153 people under surveillance as it seeks to control a new Ebola outbreak in the capital more than two months after the country was declared free of the virus, health officials said.

Three Ebola cases emerged in Liberia on Friday. The first of the new patients was a 15-year-old boy called Nathan Gbotoe from Paynesville, a suburb east of the capital Monrovia. Two other family members have since been confirmed as positive and they are all hospitalized.

"We have three confirmed cases and have listed 153 contacts, and we have labelled them as high, medium and low in terms of the risk," Liberia's Chief Medical Officer Dr. Francis Kateh told Reuters late on Saturday.