Gunmen attacked a facility treating Ebola patients in Monrovia, Liberia, on Saturday, and some patients fled, Liberian National Police spokesman Sam Collins told CNN Sunday.
No one was injured in the attack, he said.
All patients who ran away had Ebola, according to Collins, and some chose to stay at the facility.
Since an Ebola epidemic was declared in Guinea in March, the disease has spread to Sierra Leone, Liberia and Nigeria.
In the deadly disease's current outbreak in West Africa, 712 people have died from Ebola and 1,310 people are confirmed to be infected with the virus, the World Health Organization reports.
Ebola is spread through contact with organs and body fluids such as blood, saliva, urine and other secretions of infected people.
Last week, Liberia's government said that sample doses of ZMapp, an experimental drug used to treat two American healthcare workers in Atlanta, Georgia, would be sent to Liberia to treat doctors who have contracted the virus.
The country had requested the drug, and the White House and U.S. Food and Drug Administration approved it.
ZMapp has not been tested for public use. Earlier, the company that makes ZMapp said its supply was exhausted after fulfilling a request of a West African country which it did not, at the time, name.
In late July, Liberia closed most of its borders in an effort to contain the spread of the disease.