(MENAFN- AFP) Liberia has released its last two known Ebola cases from hospital and started the countdown to being declared free of the virus for a third time, authorities said on Friday.

The patients, released from a treatment unit (ETU) in the capital Monrovia on Thursday, are the father and younger brother of a 15-year-old boy who died on November 23.

"As far as we know (there is) no case in the ETUs in the entire republic of Liberia," Tolbert Nyensuah, head of the country's Ebola response, told state radio.

"We also know that there is no new known transmission as of today, based on our epidemiological investigations."

Nyensuah said 165 potential contacts of the family -- 34 of them high-risk -- are going into the third week of the 21-day observation period, with none showing signs of illness.

Liberia was the last country affected by the two-year west African outbreak, with Sierra Leone declared free of transmission in November and Guinea's last known case recovering two weeks ago.

The patients' recovery triggered a 42-day countdown -- twice the incubation period of the virus -- before Liberia can be declared free of transmission for a third time.

Ebola has left more than 11,300 people dead since December 2013 in its worst ever outbreak. Liberia has registered almost 10,700 cases and more than 4,800 deaths.

The country was first declared free of human-to-human transmission in May, only to see the fever resurface six weeks later, and officially credited with beating the epidemic for a second time in September.