Liberia has been the hardest hit by the epidemic, with 2,458 deaths out of 4,249 cases, according to World Health Organization figures. The disease has claimed nearly 4,500 lives overall in west Africa.
Transport Minister Angela Cassell-Bush said she had quarantined herself after her personal driver became sick.
"I did not have any direct contact with him but I am doing it by precaution," she said in a statement, adding that she would stay away from work for 21 days under agreed protocols.
Liberia's chief medical officer, Bernice Dahn, meanwhile said she had returned to work on Monday after being placed in quarantine for 21 days following the death of her deputy last month.
Also Read
International efforts increased to help the worst-hit countries of Liberia, Sierra Leone and Guinea, after the UN Security Council on Wednesday called for efforts to "accelerate and dramatically expand" aid to stop the epidemic.
The Liberian presidency said that Germany had promised to take charge of an Ebola treatment centre being built by the WHO in Paynesville, an eastern suburb of Monrovia.
Lindner also said that more than 3,000 people in Germany had volunteered to fight Ebola in Liberia, it added.
In neighbouring Sierra Leone, President Ernest Bai Koroma sought help with testing during a visit by the administrator of USAID, Rajiv Shah, and Norwegian Foreign Minister Boerge Brende yesterday.
"We need to increase the capacity of our laboratories so they can treat 500 to 600 samples a day, as quickly as possible," Koroma said in a statement.
All three worst hit countries are still far from their current targets for treating the disease.