Forty-eight travelers who have returned to Minnesota from Ebola-stricken nations in West Africa are being monitored by state health officials for 21 days to make sure they don't have any signs of the deadly virus, the Minnesota Department of Health reported Wednesday.

All the travelers are considered low risk, according to the Health Department, meaning they might have been visiting relatives in Liberia, Guinea or Sierra Leone but never came in contact with an Ebola case. None was in the "some" or "high" risk categories of medical or relief workers who had potential contact with an infected patient's blood, saliva or other bodily fluids.

Voluntary monitoring involves twice-daily phone calls between state health officials and the travelers, who are checking their body temperatures and any changes in their physical health that could suggest an Ebola infection.

Similar systems were implemented by the U.S. Centers for Disease Control and Prevention in the six U.S. states with the most travelers from the affected nations.

Minnesota — with its large population of Liberian natives — receives the seventh most travelers and was next in line. Monitoring in the state started when Gov. Mark Dayton announced the program Oct. 27. The state will provide weekly updates on its monitoring activities.

Wednesday's report cited an additional 12 people who either returned recently and still are being contacted, or haven't been located yet because of inadequate or incorrect contact information.

Kris Ehresmann, infectious disease director for the state Health Department, said she doesn't believe the travelers intentionally provided bad information to avoid state monitoring.

Travelers who develop fever or fatigue would be subject to further restrictions — perhaps isolation in special Ebola treatment hospital units — in order to provide them medical care and to reduce the risk of spreading the virus.

Minnesota's approach was unveiled last week as an alternative to more restrictive and controversial isolation policies enacted in New York, New Jersey and other states.

Most travelers have appreciated the contact with public health officials, Ehresmann said.

"They're very receptive," she said, "and very grateful for the program."