The nurse who has resisted state-imposed quarantines after she treated Ebola patients in Africa went out for a bike ride in northern Maine on Thursday in a show of defiance as state health officials considered seeking a court order to enforce her isolation.

Kaci Hickox, 33 years old, went biking in rural Fort Kent, confirmed Steven Hyman, one of her lawyers. Local media tweeted photos of a police car following Ms. Hickox as she cycled along a quiet road in the sparsely populated reaches of the state. "I wish the police car well, and she can go for a bike ride," Mr. Hyman said. "Hopefully, that won't make her public enemy No. 1."

Maine officials said Wednesday that state police would monitor her if she leaves her home. But she can't be detained until the state seeks a court order and the order is signed by a judge. Mr. Hyman said he wasn't aware of any court order filed Thursday morning.

State health officials couldn't be reached for immediate comment Thursday.

Ms. Hickox has become the public face of the U.S. domestic response to the Ebola crisis since she landed in New Jersey on Friday after a five-week stint with Doctors Without Borders in Sierra Leone. She was quarantined in a tent in Newark until she was allowed to return home Monday amid her complaints about the necessity of the confinement and conditions at the hospital.

She says she has no symptoms of the disease and won't comply with a request that she voluntarily stay home until Nov. 10, when the 21-day Ebola incubation period would end.

"I'm not willing to stand here and let my civil rights be violated when it's not science-based," she told reporters outside her home near the Canadian border late Wednesday. She said she would continue to monitor her temperature and watch for symptoms: "It is not my intention to put anyone at risk in this community," she added.

Write to Jennifer Levitz at jennifer.levitz@wsj.com

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