Saturday's attack sparked fears that items carried away from the clinic would accelerate the spread of the deadly, highly contagious infection.
While Assistant Health Minister Tolbert Nyenswah said all 29 patients who had been at the center in Monrovia's densely populated West Point township had been moved to the city's John F. Kennedy Memorial Medical Center.
Williams said 17 of the patients escaped, three were taken by their relatives and nine others had already died.
The attack on the center is a major setback for the efforts to combat the spread of the disease in Libera, particularly in West Point, a slum where more than 50,000 people are believed to reside. Ebola is spread by bodily fluids, including sweat and blood, and the looting of bedding as well as the escape of infected patients into the population could worsen the spread of the disease in a skeptical community.
At the end of last week, the World Health Organization said the death toll in the ebola outbreak had risen to 1,145. At least 2,127 cases have been reported from its start in Guinea in February, Sierra Leone, Nigera and Liberia. More than 400 of the dead are in Liberia.