Seven American aid workers who had been in Congo to combat the Ebola outbreak are now quarantining at a new isolation facility in Kenya following US government travel restrictions, the head of a US charity employing them stated.

The aid workers represent the first known individuals to quarantine at the facility, which has drawn significant opposition in Kenya and remains central to a legal case where a court ordered work to be suspended. Construction proceeded anyway, based on statements from US officials and satellite imagery analysis.

Washington's updated policy requires American citizens returning from the Democratic Republic of Congo, site of an Ebola outbreak, to spend three weeks in a third country before entering the United States.

The US government is constructing the 50-bed bio-isolation unit on an air force base in central Kenya to house asymptomatic Americans exposed to the virus in the Democratic Republic of Congo or Uganda. Many Kenyans express anger over what they view as the US shifting the associated health risks.

Last month, Kenya's health minister announced an immediate halt to the facility's construction after being found in contempt of court for not following the order to stop work pending a final ruling.

"Samaritan's Purse has seven American Disaster Assistance Response Team staff members there," Franklin Graham, president and CEO of Samaritan's Purse, told reporters in response to inquiries.

"None of them have any symptoms, but they are being quarantined by the Kenyan government for 21 days," Graham said.

Aid workers under US health observation

A US State Department official indicated that a group of asymptomatic Americans who had worked on the front lines of the Ebola response had "voluntarily moved to the Kenya facility for precautionary monitoring and isolation."

"Kenyan authorities have authorized their movement into the facility under the observation of the US Public Health Service clinicians," the official said, noting the decision was made "strictly out of an abundance of caution."

Kenyan health ministry officials did not immediately respond to calls or requests for comment on the move. A senior Kenyan foreign ministry official stated they had no information on it.

Another source familiar with the matter who requested anonymity said that the group had arrived at the site in central Kenya on Monday and were sleeping in army cots in tents.

The source noted some had treated Ebola patients at the Christian aid group's treatment centers in Congo, while others performed tasks such as construction with no direct contact with the sick.

"There is one potential high-risk exposure," the source said, adding that their health was being monitored. Kenyan authorities are not permitting the group to leave the facility and travel elsewhere in the country.

The often fatal viral disease spreads through direct contact with bodily fluids from infected people or animals.

Calls for treatment in Kenya

Samaritan's Purse, which has been promised several million dollars from the Trump administration for the Ebola response, is an evangelical Christian group that operates in disaster zones around the world.

It is one of the largest foreign aid groups treating Ebola in Congo and has the biggest number of Americans there, working closely with the World Health Organization to contain the outbreak.

One of its US staff members who contracted Ebola earlier this month was transferred to a hospital in Germany on Monday. The State Department official said any decisions on treatment would be handled on a case-by-case basis.

There is no proven treatment for or vaccine against the rare Bundibugyo species of the virus, which has already killed at least 828 people since mid-May, and the World Health Organization says it is still spreading largely undetected.

Graham, who had criticized the travel restrictions, said he would like Americans who catch Ebola to receive treatment in Kenya, after members of the group toured the facility this week.

"It is a state-of-the-art facility. If somebody did get sick, that is the place you want to take them," he said.