The U.S. State Department on Thursday ordered the departure of all family members at its embassy in Liberia, one of the four West African nations hit hard by the Ebola virus.

"The State Department today ordered the departure from Monrovia of all eligible family members not employed by post in the coming days," department spokesperson Marie Harf said in a statement.

She said the U.S. Embassy in Liberia suggested the step "out of an abundance of caution," adding that "Washington was focusing its efforts on helping U.S. citizens in the country as well as the Liberian government, international health organizations and local non-governmental organizations to deal with the unprecedented Ebola outbreak."

Meanwhile, additional disease specialists, including 12 disease prevention specialists from the U.S. Centers for Disease Control and Prevention and a 13-member Disaster Assistance Response Team, were sent to Liberia.

The State Department also warned the U.S. nationals not to travel to Liberia.

The Ebola outbreak in March has sickened 1,711 people and killed 932 so far in Guinea, Liberia, Nigeria and Sierra Leone, according to the World Health Organization (WHO). The virus is spread through direct contact with the bodily fluids of those infected.

Liberia and Sierra Leone account for more than 60 percent of the deaths, according to the WHO.